Lemons (not to be) sweet.
Lemons aren't sweet.
You (to be) interested in football.
You are interested in football.
An elephant (to be) a big animal.
is
It (to be) cold today.
is
Mr and Mrs Jones (to be) teachers.
are
They (not to be) thirsty, they (to be) hungry.
are not/aren't....are
He (not to be) married.
He isn't married.
This exercise (not to be) difficult.
is not/isn't
Hockey (not to be) a slow game. It (to be) fast.
is not/isn't....is
Amy (to be) 5 years old.
Amy is 5 years old.
She (to be) very tired.
is
Mice (not to be) big animals.
are not/aren't
Your classmates (to be) friendly.
Your classmates are friendly.
Washington (to be) in America.
is
Europe and Africa (to be) continents.
are
I (not to be) a teacher. I (to be) a student.
am not/ 'm not....am
Dogs (to be) man's best friend.
are