If употребляется в придаточном предложении, а would в главном.
Вроде, пишится Сабжект :)
This milk may go off if you don't put into the fridge.
перевод: Это молоко может испортиться если ты не поставишь его в холодильник.
The Town Mouse likes to play computer games .
A: What should I do if I see grenade?
B: I think you should call the police, so that they understood what was happening. You can not take in hands or stick into it.
A: How can I call the police?
B: How about call 112 - a system providing call emergency services on a single number "112" on the territory of the Russian Federation.