Tìm x biết x chia hết cho 7. 21

A. $x\in \left\{21, 22, 23,24, 25, 26\right\}$

B. $x\in \left\{22, 23, 24, 26, 27, 28\right\}$

C. $x\in \left\{21, 22, 23, 24, 25, 26, 27\right\}$

D. $x\in \left\{22, 23, 24, 25, 26, 27\right\}$