A、 The impact of enzymes on chemical reactions.
B、 The way the body produces enzymes.
C、 The structure of enzymes.
D、 Types of chemical products created with enzymes.

【正确答案】 A

【答案解析】解析：由文中原句“Before I go on to the biochemical specifics of how this works”可知教授整段都要说明作用是加速身体内的各种生物化学反应，所以文章的主旨是说明酶的作用，故选A。

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.

【正确答案】 B

【答案解析】解析：由文中原句“That’s because the chemical structure of the enzyme itself does not become altered as if enables the reaction”可知酶参与到生物化学反应中时自身的结构是不会改变的，故选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：由文中原句“enzymes greatly reduce the amount of energy required to start the reactions”可知酶可以减少生物化学反应时所需的能量。故选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：由文中原句“Before I go on to the biochemical specifics of how this works，let me provide a figurative example”可知教授说道锁和钥匙的例子，是为了证明酶的重要性，故选A。

A、 Enzymes are what make many of the body's biochemical reactions possible.
B、 Enzymes are what make many of the body's chemical reactions possible.
C、 Enzymes are what make many of the body's reactions possible.
D、 Enzymes are what make many of the body's biochemical reactions impossible.

【正确答案】 A

【答案解析】解析：由文中原句“Enzymes are what make many of the body’s biochemical reactions possible”可知酶是一种能够使身体中的大多数生物化学反应顺利进行的物质，故选A。