Answer
(a) Scalar
(b) Vector
(c) Vector
(d) Scalar
Work Step by Step
(a) Time is always a scalar (no direction required).
(b) For displacement a direction is required.
(c) $average~velocity=\frac{displacement}{time}$. But, displacement is a vector. So, velocity is also a vector.
(d) $average~speed=\frac{distance}{time}$. But, distance is a scalar. So, average speed is also a scalar.
