3 Fill in the gaps with a/an where necessary. 1) There is
new English book on the desk.
2) She's got
curly hair.
3) Simon has got
moustache.
4) She is drinking
cup of tea.
5) Sandra is ____ architect.
6) The Maasai are
tribe.
7) She usually wears heavy earrings.
8) Look! There are mice running.
9) My sister is
honest person.
10) My son wants to be
astronaut.

Sure, I'd be happy to help fill in the gaps with 'a' or 'an' where necessary. Here are the sentences with the appropriate articles inserted:

1. There is a new English book on the desk.
2. She's got curly hair. (This sentence is correct as is; no article is needed.)
3. Simon has got a moustache.
4. She is drinking a cup of tea.
5. Sandra is an architect. (Use 'an' because 'architect' starts with a vowel sound.)
6. The Maasai are a tribe.
7. She usually wears heavy earrings. (This sentence is correct as is; no article is needed.)
8. Look! There are mice running. (This sentence is correct as is; no article is needed.)
9. My sister is an honest person. (Use 'an' because 'honest' starts with a vowel sound.)
10. My son wants to be an astronaut. (Use 'an' because 'astronaut' starts with a vowel sound.)

Remember, the choice between 'a' and 'an' depends on the initial sound of the following word. 'A' is used before words that begin with a consonant sound, while 'an' is used before words that begin with a vowel sound.