Speed is defined as rate of change in position or we can say it is ratio of total distance moved in total interval of times
While in order to find the velocity we know that it is ratio of total displacement and total time
so here main difference is that speed is scalar quantity and we do not require any direction in speed while in velocity we require direction as well as magnitude
Here we need to select a case where speed is constant while velocity is not constant.
It is only possible when direction is continuously changing but magnitude remains the same
so here correct answer will be
C) driving around in a circle at exactly 100 km/hr
