Question 26: The correct option is: B. If he doesn't prepare, he may not do well on the presentation.
Explanation: "doesn't prepare" is the correct negative form for the present tense, and "do well" is the proper phrase to describe performance in this context.

Question 27: The correct option is: B. I want to finish my work early, so I won't delay my study time.
Explanation: "want to finish" is the correct structure, and "won't delay" fits the future action correctly.