Answer:
(c) 8x -16
Explanation:
The outside factor multiplies each of the terms inside parentheses.
4(2x -4) = 4(2x) +4(-4) = 8x -16
_____
Additional comment
You can think of parentheses as a "bag". The factor outside tells you how many bags you have. When you dump that many bags (eliminate parentheses), you find that the number of each of the kinds of contents is the number in one bag, multiplied by the number of bags.
If you have 4 bags that each have 2 apples and 4 oranges, your total is 8 apples and 16 oranges.