5Can I say both: Yes
A young couple decides to buy a car. ---> I'd choose this one.
A young couple decide to buy a car.
Can I treat "a couple" like "a team", "a family"? Yes
I've got one more problem with the verb:
The highlight for me was the special effects.
The highlight for me were the special effects. ---> I'd choose this one.
The subject of the verb ('was') is the singular noun ''highlight'.
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