<span>The sentence which does not contain any errors in comma usage is:
D. Nobody signed up for the auditions, however.
In this sentence, it is proper to put comma just before the word "however" to highlight the usage and purpose of this conjunction.</span>
The answer is 2.
Enzymes work to speed up chemical reactions by changing what goes into the reactions (substrates) into different molecules. To do so, these enzymes bind with the substrates, making the physical form very important. The lock and key method explains that enzymes and their corresponding substrates are shaped very specifically to be able to fit into one another to undergo this change.
