Answer:
The molecules or ions in a solution can freely intermingle.
Step-by-step explanation:
The reactant molecules and ions can move freely in solution, so thy are more likely to collide with each other and form products.
A is wrong. Solutions are homogeneous.
B and C are wrong. The statements are correct, but they are not the reason why reactions are carried out in solution.
D is wrong. Chemical reactions do not always produce a colour change.
F is wrong. Some chemicals react with water, so other (often flammable) solvents must be used.