In the expression a + 2b − 12c2, a, 2b, and −12c2 are examples of

Terms

Explanation:
Any expression is formed of terms separated by addition or subtraction.
A term can be a number, a variable or the product of multiplying a number and a variable.
Now, the given expression is:
a + 2b + 12c^2
This expression has three terms all separated by addition. These terms are:
a : which is only a variable
2b : which is the product of a number and a variable
12c^2 : which is the product of a number and a variable

Hope this helps :)

Idon't know the answer