The students will have Science instead ..... Maths. The Maths teacher

The students will have Science instead ..... Maths. The Maths teacher has fallen ill.
a) off b) of c) from
There are plenty ... ways to cook this tasty dish.
a) of b) on c) in
Carol was responsible .... the rare tropical plant, wasn*t she?
a) on b) at c) for
Could you help me ..... my homework? Yes, i will try.
a) on b) with c) of
The students felt sorry ... their new classmate.
a) of b) for c) on
May i come .... ? Yes, you may.
a) out b) on c) in