Learn English – Which of these two sentences is correct (“processes” vs. “process”)

Just as we can speak of a two-man canoe, we can speak of a two-player game. Best to use the hyphen, though.

"A" is singular: You can't use "cars" and "arms." "A red car and a blue car" and "a left arm and a right arm" indicate two cars and two arms. "Red and blue cars" and "left and right arms" have indeterminate numbers.