A、 It divides into two different parts.
B、 It keeps the same chemical structure.
C、 It becomes part of a new chemical compound.
D、 It produces more of the enzyme(酶).

【正确答案】 B

【答案解析】解析：细节题。根据讲座内容及结尾的That’s because the chemical structure of the enzyme itself does notbecome altered as if enables the reaction．So a single enzyme can be used to start the same biochemical reactionover and over again．可知．教授指出酶在生化反应中保持不变的化学结构。因此，正确答案为B。

A、 Provide extra energy to start the reaction.
B、 Raise the temperature of the chemicals.
C、 Release a chemical needed to start the reaction.
D、 Lower the amount of energy needed to start the reaction.

【正确答案】 D

【答案解析】解析：细节题。根据Now，there are two reasons that enzymes are so effective at enabling biochemical reactions．First enzymes greatly reduce the amount of energy required to start the reactions可知，酶通过较少能量帮助开启生化反应。因此，正确答案为D。

A、 To show that enzymes are very effective.
B、 To point out that enzymes can sometimes fail to work.
C、 To explain what enzymes are made of.
D、 To describe different types of enzymes.

【正确答案】 A

【答案解析】解析：细节题。根据Enzymes act like your hands，quickly allowing chemical reactions that would otherwise takemuch longer．Now，there are two reasons that enzymes are so effective at enabling biochemical reactions．可知，教授提及锁和钥匙主要是为了表明酶很有效。因此，正确答案为A。