Modals Could and Couldn't

When I was young, I __________ play the guitar: it was too difficult for me!

Yesterday, Peter ____________ do that exercise alone. So, he called me for help.

In 1950, people __________ use mobile phones.

We ___________ open the door: it was locked from the inside!

In 1900, people _________ watch TV.

Mary's grandfather _________ play chess and he was the best!

Peter ___________ play tennis last Monday: he had broken his arm!

When I was young, I __________ play the guitar: it was too difficult for me!

Yesterday, Peter ____________ do that exercise alone. So, he called me for help.