It looks like you need to fill in the blank in the sentence you provided. Based on the context, an appropriate word to complete the sentence could be "seep," as it suggests that the smell is gradually spreading into the other classrooms.
So, the complete sentence would read: "Something was going terribly wrong in the science lab, and the smell was beginning to seep into the other classrooms in the hall."
If you have a list of options to choose from, please provide them for a more specific answer!