to verb or verbing

I can’t imagine Peter (a)   (go) by bike.

He agreed (a)   (buy) a new car.

The question is easy (a)   (answer).

The man asked me how (a)   (get) to the airport.

I look forward to (a)   (see) you at the weekend.

Are you thinking of (a)   (visit) London?

We decided (a)   (run) through the forest.

The teacher expected Sarah (a)   (study) hard.

She doesn’t mind (a)   (work) the night shift.

I learned (a)   (ride) the bike at the age of 5.