Could, couldn't, will be able to, won't be able  ...

I _______________ understand Jane because I could speak German.

My dad _______________ go to work because he was ill.

In the future robots _______________ have conversation with us.

I was so tired that I _______________ sleep immediately.

We _______________ play tennis because the weather was bad.

We _______________ control our future houses with our voices.

She ¬¬_______________ go on holiday next month if her parents give her permission.

Tom _______________ listen to music because his CD player was broken.