Modal verb: Be able to
My favourite cousin ...................... come to my wedding. I was so happy!
My favourite cousin 'was able to' come to my wedding. I was so happy!
............ people .................. travel to other planets 50 years from now?
'Will' people 'be able to' travel to other planets 50 years from now?
My parents ................ look after my baby brother during the day. He has got a babysitter.
My parents 'aren't able to' look after my baby brother during the day. He has got a babysitter.