What does a reviewer do during peer-review?

A. Focus on mistakes in spelling.

B. Change data to support results.

C. Check for mistakes and bias.

D. Repeat the experiments in the article.

A and C. If it's a peer-review you are most likely going over it and checking everything is correct, that there is nothing wrong you wouldn't repeat the experiments unless the instructions for them were to create a experiment and give it to someone to repeat/do. You wouldn't change the data they would. So in a way it is also B.