You _____ (go) to the doctor if you're feeling sick.
should
John forgot his homework. What should he have done?
He should have remembered to do his homework.
Can é usado para falar de habilidades no presente.
Verdadeiro
What should you do if you miss the bus?
I should wait for the next bus or find another way to get to my destination.
Eu posso ajudar você.
I can help you.
If I had more time, I _____ (travel) around the world.
could
Anna wants to improve her English. What can she do?
She can take an English course or practice speaking with native speakers.
Could é apenas o passado de can.
Falso (pode ser usado para pedidos educados e possibilidades)
Could you lend me a pen, please?
Yes, I could. Here you go.
Ela deve estudar para o exame.
She should study for the exam.
She _____ (speak) three languages fluently.
can
It's late and dark outside. Should you walk home alone?
No, you shouldn't. It's safer to call an uber or ask someone to accompany you.
May é mais forte que must em termos de obrigação.
Falso (must é mais forte que may)
May I leave the table?
Yes, you may.
Nós poderíamos ir ao parque amanhã.
We could go to the park tomorrow.
You _____ (bring) an umbrella. It looks like it will rain.
might
Your friend is very tired. What ought he to do?
He ought to get some rest and go to bed early.
Might expressa uma possibilidade mais incerta que may.
Verdadeiro
What might happen if you don't study for the test?
I might fail the test.
Ele pode estar dormindo agora.
He might be sleeping now.
He _____ (finish) the project by tomorrow if he works hard.
could
You have a big exam tomorrow. What must you do tonight?
You must study and get a good night's sleep.
Should e ought to têm significados muito diferentes.
Falso (são usados de forma similar para dar conselhos)
What must you do before traveling abroad?
I must check my passport, pack my bags, and make sure I have all the necessary documents.
Você deve usar o cinto de segurança.
You must wear a seatbelt.