Write the sentences in the third person singuiar. пример: they are taking pictures now. he is taking pictures now. the birds are flying now.

The birds are flying now. - The bird is flying now.
или 
It is flying now. - потому что птицы и животные в единственном числе обозначаются местоимением it.
Но Вы можете написать:
She is flying now. - если птичка, о которой Вы спрашиваете, из сказки, потому что в сказках мы как бы "оживляем" сказочные персонажи животных и птиц и говорим о них, как и о людях - в единственном числе: he или she.

Healthy lifestyle

If you want to be healthy you must keep a healthy lifestyle. You must get up early and do exercises. Then you must take a cold shower. You must have breakfast and it must be health food. You have to drink milk, eat much vegetables and fruit. And you must eat less bread, sugar or fast food. You have to go for sport. You have to move as much as possible. You have to walk, dance. You must walk in the forest. You have to swim in the river or in the lake.

Если вы хотите быть здоровым, вы должны вести здоровый образ жизни. Вы должны вставать рано и делать упражнения. Вы должны принять холодный душ. Вы должны позавтракать, и это должно быть здоровое питание. Вы должны пить молоко, есть много овощей и фруктов. И вы должны есть меньше хлеба, сахара или фаст-фуда. Вы должны заниматься спортом. Вы должны двигаться как можно больше. Вы должны ходить, танцевать. Вы должны идти в лес. Вы должны купаться в реке или в озере.

2 1.know 3 1.have

2.works 2.is working

3.came 3.forgets

4.has 4.is coming

5.eat 5.goes

6.is listening 6.are singing

7.goes 7.finish or finished

8.eats 8.are playing

9.is shopping 9.read

10.like 10.buys

23 1.Where are my keys?

2.What time do you get up?

3.What are you doing in my room?

4.Jack have many lessons on Monday.

5.Where do you live?

6.Sally likes black coffee.

7.Do you go with us?

8.He knows my father.

9.She is having lunch at the moment.

10.I don't know his name.

11.She doesn't play tennis well.

12.Look at him!He is swimming to the rock.

13.Jack is in the yard.He Is washing his car.

14.Sid doesn't skate well

15.He usually plays piano after dinner.

16.Jane is having dinner now.

17.Are you a pupil from our school?

18.We are at the shopping center.

19.Every Sunday my father takes me to the Zoo.

20.What do they do usually in the evening.

18 1.is sleeping

2.is listening

3.likes

4.Are you working

5.are you doing

6.do you usually have

7.go

8.watch

9.is making

10.often reads