1) It is because they produce a lot of pollution in the atmosphere
2) They are limited in number and can't be recycled
Hope this helps!
Answer:

Downward
Explanation:
We are given that
Mass of monkey=12.8 kg
Tension=156 N
We have to find the magnitude of the elevator's minimum acceleration.

Where 
Substitute the values



Hence, the acceleration =
Direction of the elevator's minimum acceleration is downward because the elevator moves downwards.
I think it's Barium sulfate, the soild and percipitate