When dealing with uncountable nouns (like "music" or "happiness"),
we use singular verb forms:

is	(not are)
was	(not were)
has been	(not have been)
does / goes / feels ...	(not do / go / feel)

Choose the correct verb form. Pay attention to whether the noun is countable or uncountable.

1. My teeth ___ hurting.
is
are

2. This music ___ too heavy and gloomy for my liking.
is
are

3. The crisis ___ avoided, thanks to your quick wits.
was
were

4. The fish ___ swimming together in the pond in one fishy gang.
was
were

5. A swarm of suspicious-looking butterflies ___ been seen flying in the area.
has
have

6. The amount of emissions ___ decreased rapidly after the introduction of electric cars.
has
have

7. There ___ several reasons why someone would do such a silly thing.
is
are

8. The old gym equipment ___ fully replaced last year.
was
were

9. The sheep ___ all grazing (laiduntaa) in the lush green fields.
is
are

10. The flock (lauma) of sheep ___ seen here yesterday, followed by their shepherd.
was
were