3.1

2 's / is waiting
3 're / are playing
4 He's / He is lying
5 They're / They are Having
6 She's / She is sitting

3.2

2 's / is cooking
3 're / are standing
4 is swimming
5 're / are staying
6 's / is having
7 're / are building
8 'm / am going


3.3

3 She's / She is sitting on the floor.
4 She's not / She isn't reading a book.
5 She's not / She isn't playing the piano.
6 She's / She is laughing.
7 She's / She is wearing a hat.
8 She's not / She isn't writing a letter


3.4

3 I'm sitting on a chair. or 
  I'm not sitting on a chair
4 I'm eating. or I'm not eating.
5 It's raining. or It isn't raining. / It's not raining.
6 I'm learning English.
7 I'm listening to music. or I'm not listening to music.
8 The sun is shining. or The sun isn't shining.
9 I'm wearing shoes. or I'm not wearing shoes.
10 I'm not reading a newspaper.