What is the angle between the two hands of a clock at $3$ o'clock ?

Given: Time in the clock $=3$o'clock

At $3$ pm, the minute hand of a clock is at $12$ and the hour hand is at $3$

We know that each division of the clock represents $30°$

And the no. of division between the two hands of a clock at $3$ pm is $3$ divisons

Therefore, the required angle is $3\times 30°=90°$

Hence, the correct option is D.