Answer
The correct answer is (c): Smaller, larger and larger.
Work Step by Step
1. They have the same magnitude of charges, but K has a larger radius than Li, therefore, $KF$ should have smaller lattice energy than $LiF$.
2. They have the same magnitude of charges, but Cl has a larger radius than F, therefore, $KF$ should have larger lattice energy than $KCl$.
3. They have the same magnitude of charges, but I has a larger radius than F, therefore, $KF$ should have larger lattice energy than $KI$.
