Which of these functions has period 7?

A)y= cot 7/pi x

B)y= tan pi/7 x

C)y= sin 7/pi x

D)y= cos pi/7 x

period of cos kx = 2pi/k

so,
2pi/k = 7
k = 2pi/7

period of tan,cot = pi, so
(B)