Question 1
What makes a mixture homogeneous?
The right answer is the one marked above.
It has the same composition throughout. Every part of it, however small, holds the components in the same proportions as every other part.
Holding one substance only would make it a pure substance, not a mixture at all. A homogeneous mixture can still be separated — that is the whole of section 3.3 — and copper sulphate solution is homogeneous and bright blue.