Can/can't & have to

Every May, in the UK, someone throws a cheese from the top of Cooper's Hill and runners (a)   (try) and catch it.

There (a)   (be) more than 15 runners in a race because people often fall down and have accidents.

The Colorado Pack Burro race is a marathon with a difference. Each runner 3 (a)   (lake) a donkey up a 29-mile path.

However, there's one important rule — they (a)   (push) the donkey, pull the donkey or even carry the donkey, but they can't ride it.

In the wife-carrying race in Finland, runners (a)   (carry) their wives along a 253.5 meter track.

The wife (a)   (run) at all, only the man can.

She (a)   (be) the runner's own wife — it's OK if she's a friend's wife, for example.