Образуйте множественное число от следующих существительных : a friend, a doctor, a pilot, a driver,a sister, a son, a brother, a pupil,a mother, a cat

i ( read) books in the evening.

i ( do not to read) books in the morning.

i (am writing) an exercise now.

i (am not   writing) a letter now.

i ( sent) a letter to my friend yesterday.

he (did not   spend) last summer in the country.

is my little sister ( sleeping) now?

my little sister (was sleeping) at this time yesterday.

when nick came home yesterday, his brother (was playing) with his toys.

they (were drinking) tea, when i ( came) home.

i have already (done) my homework. now i can go for a walk.

did you ( play) the piano yesterday?

are you (   playing ) the piano today?

where did you ( put) my pen? i cannot find it.

he has already ( solved) the problem.

i ( finished) my work at 7 yesterday.

i (had finished) my work by 7 yesterday.

when i ( came) home, mother had already ( cooked) dinner.

lanny ( says) that he ( got) his education in cape town.