Phân tích giúp về code tạo trắc nghiệm

<p><script type="text/javascript">var dapan_array=new Array("C","D","C","A","C","B","D","D","D","C");</script>1) ___ that as both birds and mammals become larger, their metabolic rates er unit of tissue decrease, and they generally live longer.<br /><br /><input id="choice1A" value="A" name="choice1" type="radio"><label id="C1A">a) The truth</label><br /><input id="choice1B" value="B" name="choice1" type="radio"><label id="C1B">b) If true</label><br /><input id="choice1C" value="C" name="choice1" type="radio"><label id="C1C">c) It is true</label><br /><input id="choice1D" value="D" name="choice1" type="radio"><label id="C1D">d) To be true</label><br /><br />2) Asteroids are small and therefore very difficult to identify, even when ___ to Earth<br /><br /><input id="choice2A" value="A" name="choice2" type="radio"><label id="C2A">a) quite closely</label><br /><input id="choice2B" value="B" name="choice2" type="radio"><label id="C2B">b) are being quite close</label><br /><input id="choice2C" value="C" name="choice2" type="radio"><label id="C2C">c) are they quite closely</label><br /><input id="choice2D" value="D" name="choice2" type="radio"><label id="C2D">d) they are quite close</label><br /><br />3) A number of modern sculptors have rejected ___ of minimal and environmental art and developed a style of extreme realism.<br /><br /><input id="choice3A" value="A" name="choice3" type="radio"><label id="C3A">a) which abstract qualities</label><br /><input id="choice3B" value="B" name="choice3" type="radio"><label id="C3B">b) there are abstract qualities</label><br /><input id="choice3C" value="C" name="choice3" type="radio"><label id="C3C">c) the abstract qualities</label><br /><input id="choice3D" value="D" name="choice3" type="radio"><label id="C3D">d) the qualities are abstract</label><br /><br />4) ___ tributaries of the Mississippi River system were navigated by steamboats during the period before the outbreak of the Civil War<br /><br /><input id="choice4A" value="A" name="choice4" type="radio"><label id="C4A">a) More than forty</label><br /><input id="choice4B" value="B" name="choice4" type="radio"><label id="C4B">b) More than forty were</label><br /><input id="choice4C" value="C" name="choice4" type="radio"><label id="C4C">c) Forty more than</label><br /><input id="choice4D" value="D" name="choice4" type="radio"><label id="C4D">d) There were more than forty</label><br /><br />5) Mary Eliza McDowell’s introduction to social service came ___, when she assisted victims of the great Chicago Fire of 1871<br /><br /><input id="choice5A" value="A" name="choice5" type="radio"><label id="C5A">a) was sixteen years old</label><br /><input id="choice5B" value="B" name="choice5" type="radio"><label id="C5B">b) had sixteen years</label><br /><input id="choice5C" value="C" name="choice5" type="radio"><label id="C5C">c) at age sixteen</label><br /><input id="choice5D" value="D" name="choice5" type="radio"><label id="C5D">d) sixteen</label><br /><br />6) Young herons are helpless for a few weeks ___ they learn to fly.<br /><br /><input id="choice6A" value="A" name="choice6" type="radio"><label id="C6A">a) how</label><br /><input id="choice6B" value="B" name="choice6" type="radio"><label id="C6B">b) before</label><br /><input id="choice6C" value="C" name="choice6" type="radio"><label id="C6C">c) despite</label><br /><input id="choice6D" value="D" name="choice6" type="radio"><label id="C6D">d) since</label><br /><br />7) The history of painting is a fascinating chain of events that probably began with ___<br /><br /><input id="choice7A" value="A" name="choice7" type="radio"><label id="C7A">a) ever made the very first pictures</label><br /><input id="choice7B" value="B" name="choice7" type="radio"><label id="C7B">b) the ever made very first pictures</label><br /><input id="choice7C" value="C" name="choice7" type="radio"><label id="C7C">c) the very first ever made pictures</label><br /><input id="choice7D" value="D" name="choice7" type="radio"><label id="C7D">d) the very first pictures ever made</label><br /><br />8) The center of gravity of the human body ___ behind the hip joint.<br /><br /><input id="choice8A" value="A" name="choice8" type="radio"><label id="C8A">a) locates</label><br /><input id="choice8B" value="B" name="choice8" type="radio"><label id="C8B">b) locating</label><br /><input id="choice8C" value="C" name="choice8" type="radio"><label id="C8C">c) to locate</label><br /><input id="choice8D" value="D" name="choice8" type="radio"><label id="C8D">d) is located</label><br /><br />9) The leaves and stems of the alfalfa plant are the only parts of the plant ___.<br /><br /><input id="choice9A" value="A" name="choice9" type="radio"><label id="C9A">a) the uses for livestock fees</label><br /><input id="choice9B" value="B" name="choice9" type="radio"><label id="C9B">b) for using livestock feed</label><br /><input id="choice9C" value="C" name="choice9" type="radio"><label id="C9C">c) used for livestock feed</label><br /><input id="choice9D" value="D" name="choice9" type="radio"><label id="C9D">d) they are used for livestock feed</label><br /><br />10) ___ choose to live in or near metropolitan areas simply because they like the rapid pace of city life.<br /><br /><input id="choice10A" value="A" name="choice10" type="radio"><label id="C10A">a) So large numbers of people to</label><br /><input id="choice10B" value="B" name="choice10" type="radio"><label id="C10B">b) There are large numbers of people</label><br /><input id="choice10C" value="C" name="choice10" type="radio"><label id="C10C">c) Large numbers of people</label><br /><input id="choice10D" value="D" name="choice10" type="radio"><label id="C10D">d) Large numbers of people who</label><br /><br /><div align="center"><input language="javascript" id="button1" onclick="dapan_onclick();" value="Show answers" name="button1" type="button"></div></p>