IMO

1.Correct
2.Three years is a long time.
3. My scissors are not cutting properly.
4.The police has arrested him.
5.Fish and chips are nice to eat.(Not sure if fish and chips is a dish then is should come)
6.The rest of the staff is coming later.

Per the website https://www.better-english.com/grammar/sinplu.htm

following are the answers

1. The police is still looking for him
The police are still looking for him (police is a collective noun, so singular)

2. Three years are a long time
Three years is a long time (not sure, why three years is singular)

3. My scissors is not cutting properly
My scissors are not cutting properly (why, scissores is the name of one thing)
4. The police have arrested him (agian police is colective so singular)

5. Fish and chips is nice to eat (maybe this the UK, GMAT is in US and no such dish is here, so are)

6. The rest of the staff are coming later(Per MGMAT, prepositional subject to be avoided for verb, so staff should not be used, but rest is singular. so it should be Is not are)

Dude, the site you quoted is good to play, don't just base your studies on sites like that. Please use proper and authentic resources because whatever you learn, you must learn correct.

The police is still looking for him

Your Explanation :

The police are still looking for him (police is a collective noun, so singular)

So how can you use "are" for singular

2. Three years are a long time
Three years is a long time (not sure, why three years is singular)

Its correct , 3 yrs is used here as a collective noun of years, referring to a particular time

3. My scissors is not cutting properly
My scissors are not cutting properly (why, scissores is the name of one thing)

Please check the link below, a pair of scissors is always singular

https://en.wiktionary.org/wiki/scissors

4. The police have arrested him (agian police is collective so singular) so we will use "has"

5. Fish and chips nice to eat (maybe this the UK, GMAT is in US and no such dish is here, so are)

Correct structure = X and Y (plural verb)

6. The rest of the staff are coming later(Per MGMAT, prepositional subject to be avoided for verb, so staff should not be used, but rest is singular. so it should be Is not are

You are correct with this one.

Hope this long post helps!

gmat740 wrote:Dude, the site you quoted is good to play, don't just base your studies on sites like that. Please use proper and authentic resources because whatever you learn, you must learn correct.

The police is still looking for him

Your Explanation :

The police are still looking for him (police is a collective noun, so singular)

So how can you use "are" for singular

2. Three years are a long time
Three years is a long time (not sure, why three years is singular)

Its correct , 3 yrs is used here as a collective noun of years, referring to a particular time

3. My scissors is not cutting properly
My scissors are not cutting properly (why, scissores is the name of one thing)

Please check the link below, a pair of scissors is always singular

https://en.wiktionary.org/wiki/scissors

4. The police have arrested him (agian police is collective so singular) so we will use "has"

5. Fish and chips nice to eat (maybe this the UK, GMAT is in US and no such dish is here, so are)

Correct structure = X and Y (plural verb)

6. The rest of the staff are coming later(Per MGMAT, prepositional subject to be avoided for verb, so staff should not be used, but rest is singular. so it should be Is not are

You are correct with this one.

Hope this long post helps!

Thanks Karan. someone somewere mentioned that Police is an exception to the collective noun rule, so it will be plural.