In A/D Converter, What Is the Time Relation Between Sampling

In A/D converter, what is the time relation between sampling period T and the duration of the sample mode and the hold mode?

A) Should be larger than the duration of sample mode and hold mode
B) Should be smaller than the duration of sample mode and hold mode
C) Should be equal to the duration of sample mode and hold mode
D) Should be larger than or equals to the duration of sample mode and hold mode