AMC 8 2016 Problem 3

Four students take an exam. Three of their scores are $70, 80,$ and $90$ . If the average of their four scores is $70$ , then what is the remaining score? $\textbf{(A) }40 \textbf{(B) }50 \textbf{(C) }55 \textbf{(D) }60 \textbf{(E) }70$