Which of the following is correct?

B. Φ = 0 is false, because Φ is a null set, it is not equal to any element.

C. Φ = {0} is false, because Φ should not contain any element in the set, but here it contains an element.

D. Φ = {Φ} is also false, because null set will be considered as an element in the set.

A. {x:x² = -1, x∈Z} = Φ

For any value of x, x² will not be going to -1. So, the set will be remained with no elements. So, this set will be considered as null set

∴ option(A) is true.