Industrialization & Anthropocentric pollution or green house gases. :)
hope this helped!
I would think Canada but I do not know
A is the answerrrrrrr your welcome...
The answer is 4t, since their is no number after the plus sign you would assume that their is a one place there. you would multiply 1 by t and by -2t which would leave you with this equation; 5t+1t-2t, which is simplified into 4t