If and Unless - Quando utilizar

Quando utilizar if e unless numa frase. Unless significa exceto se ou simplesmente, significa se ... não. (Unless means except if or simply it means if...not.).

If = Se
Unless = A não ser que/A menos que

Exemplo: 
If you don't hurry, you'll be late for school again.
Unless they lower the price, I won't buy that car.
You cannot go into bars unless you are over 18.
If you don't slow down, we are going to crash.

Para aprender, somente praticando. Segue abaixo, algumas frases para praticar.

1) _____he does not find a job, his family will starve.
a) If
b) Unless
2) _____I'm late again, the teacher will be furious.
a) If
b) Unless
3) Don't interrupt the meeting_____it's an emergency.
a) If
b) Unless

Answers (respostas)

1) If  he does not find a job, his family will starve.
2) If I'm late again, the teacher will be furious.
3) Don't interrupt the meeting unless  it's an emergency