Which of the following is a vector quantity? A. Distance
B. Speed
O C. 30 m/s
D. 9.8 m/s2 down

velocity and acceleration are vector quantities

Explanation:

c and d

A.  Distance . . . . . No.  Distance is a scalar quantity.  It has no direction.

B.  Speed . . . . . No.  Speed is a scalar quantity.  It has no direction.

C.  30 m/s . . . . . No.  30 m/s is a speed without a direction, and I just told you that speed is a scalar quantity.

D.  9.8 m/s² down . . . YES !  It has a size AND a direction. It's a vector.