If c & d are positive, is d an integer

[eccentric]

If c & d are positive, is d an integer ?
i) c=d^3
ii) d=sqrt{c)

[eagleeye]

If c & d are positive, is d an integer ?
i) c=d^3
ii) d=sqrt{c)

i) c=d^3

c,d can be anything. d isn't necessarily an integer. Insufficient.

ii) d=sqrt{c)

Again, c,d can be anything. d isn't necessarily an integer.

Together:
Now From 1: c=d^3
From 2: c = d^2.

Hence d^3=d^2.
d^2(d-1)=0. Since d is positive, d is not 0. Hence d=1. So d is an integer. Sufficient.

C is correct.