Circular Track

In such type of questions get your answers from options itself.
Take 1st option and calculate distance travelled by each person so it will be (4*10)=40m for A,(4*8)=32,(4*15)=60, so here distance travelled by each person is not a Multiple of 100.
Likewise try for other options.
The correct answer is 100s

The three will never meet at the same place after they start because two people are running in the same direction with different speeds. so C will meet either A or B. but not both.