An Examination Consisting of Ten True-Or-False Questions Was Taken by a Class

Multiple Choice

An examination consisting of ten true-or-false questions was taken by a class of 100 students. The probability distribution of the random variable X, where X denotes the number of questions answered correctly by a randomly chosen student, is represented by the accompanying histogram. The rectangle with base centered on the number 8 is missing. What should be the height of this rectangle? ​ ​

A) 0.35
B) 0.25
C) 0.4
D) 0.2