AMC8 1985 Problem 7

A “stair-step” figure $1$s made up of alternating black and white squares in each row. Rows 1 through 4 are shown. All rows begin and end with a white square. The number of black squares in the 37 th row is
Image

Answer Choices
A. 34
B. 35
C. 36
D. 37
E. 38