I think the answer is either
A. Why does Harry seem sad at the end of the passage.
or
D. Where will jack and Harry find work after the professor leaves?
Reactionary force it would be
The effect of the simile in this passage makes the passage more interesting and gives it that extra "boost" to help the reader understand what is going on.
Hope this helps!
Krogstad is going to try to take his job back from Mrs. Linde, and the audience knows it, but Mrs. Linde does not know that this will happen.