1- a) he is sitting at the desk.

b) they are playing football.

c) Mary is eating dinner.

d) Ann is swimming in the club.

e) I am writing a letter.

f) you are running in the beach.

2)

a) he is not sitting at the desk.

b) they aren´t playing football

c) mary isn´t eating dinner

d) Ann isn´t swimming in the club

e) I am not writing  a letter

f) you aren´t runnig in the beach

3)  

a) is he sitting at the desk?

b) are they playing football?

c) is mary eating dinner?

d) is Ann swimming in the club?

e) am I writing a letter?

f) are you runnig in the beach?

Explicação: