2 modals expressing "ability" in the present

The thief knew the secret code. It ....................... have been someone who works here.

When the police arrest someone, they ............................. to spend a lot of time filling in forms.

The police ................................ find any evidence (NOT BE ABLE TO in the past)

Rewrite the following sentence: "It's certain that the thieves knew where the jewellery was".                          They ....................................... where the jewellery was.

You ......................... have taken your expensive watch on a camping holiday. It was very risky.

Rewrite the following sentence: "We were ordered to empty our pockets before we could go into the concert".                                   We ........................ to empty our ....

3 modals expressing "advice"

Rewrite the following sentence: "Is it OK if I take a picture of your notes?"                             .............. I take a picture of your notes?

I'm sure he ......................... be at home. He leaves work at 5 and it's 4 o'clock.

Rewrite the following sentence: "It's possible that they forgot to turn on the alarm".                  They ...................to turn on the alarm.

The past of the modal verb "can" is ...

4 modal verbs to ask for permission