Когда используется глагол связка аre ? ?

1.i was having a stroll when i saw a car accident 2. when   dad   entered the room   mother was singing а lullaby. 3. she sat down on а chair while he was painting her portrait. 4. when   we / сотеd   from the party   he was listening to   one of his records.

are they your friends? -yes, they are

is he your brother? - yes, he is

can he ride a bike? - no, he can't

do you want to play with the ball? - no, i don't

does she roller-skate well? - no, she doesn't

does your friend want to play the piano? - yes, he does