An object that completes 100 vibrations in 5 seconds has a period of
a) 0.5 second. b) 1 second. c) 2 seconds. d) none of the above choices are correct.

Explanation:

Here we are talking about the vibration frequency of an object:

(1)

The frequency   is defined as the inverse of the period (time):

(2)

Therefore the Period is:

(3)

Now, if we want to find the period we have to substitute equation (1)  in equation (3):

Finally:

>>>>This is the value of the period, which does not match with any of the options given.

Hence:

None of the above choices are correct.

chemical properties of thing