how to solve this question?

At what point(s) of R is the following function continuous? cos (x- y) . . . Choose the correct answer below. O A. {(x,y) : x = y} O B. (0,0) O C. {(x,y) : cos (x - y) # 0} O D. {(x,y) : cos (x -y) = 0} O E. The function is continuous at any point in R2. O F. The function is not continuous at any point in R2