"I'll buy you a new bicycle if you stop eating junk food,” said Lam’s mother

Lam's mother promised to buy him a new bicycle if he stopped eating junk food.

Lam's mother promises to buy him a new bicycle if he stops eating junk food.

Lam's mother will promise to buy him a new bicycle if he stops eating junk food.

Lam's mother had promised to buy him a new bicycle if he stopped eating junk food.