（求助）一数学题，看不懂意思

An even number x divided by 7 gives some quotient plus a remainder of 6. Which of the following, when added to x, gives a sum which must be divisible by?

(A) 1

(B) 3

(C) 7

(D) 8

(E) 13

实在看不懂题目的意思，xdjm们帮帮忙，谢谢。