2. What kind of changes did you observe in the gypsum itself?

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

im not exactly sure but i think its b!

it's c (engineer's do their work with mechanical stuff not on any living being)