Based on the context of your sentences, here are the appropriate answers:
A. Respire - The students began to look up and respire deeply at first and then quickly cover their noses. (This refers to breathing, which is relevant as they are reacting to a smell.)
B. Permeate - Something was going terribly wrong in the science lab and the smell was beginning to permeate the other classrooms in the hall. (This means that the smell is spreading throughout the other areas.)
So the final answers are:
- A: Respire
- B: Permeate