抑制剂
参考答案：
能使酶的必需基团或酶活性部位中的基团的化学性质改变而降低酶的催化活性甚至使酶的催化活性完全丧失的物质。
根据句意，用括号中所给单词的适当形式填空，每空一词。
小题1:Jim fell down from the tree yesterday. Luckily, he didn’t hurt (he).
小题2:— When is Teachers’ Day, do you know?
—Sure! It’s in the (nine) month of a year.
小题3:The sun shines brightly in the sky. It，s a (sun) day today.
小题4:Mom is busy cooking in the kitchen. She，s (prepare) a cake for my birthday party.
小题5:In fall, (leaf) fall down from the trees. The cold weather is coming.
作用于DNA拓扑异构酶Ⅰ的生物是（）。
A．喜树碱
B．硫酸长春碱
C．多柔比星
D．紫杉醇
E．盐酸阿糖胞苷
