I read on news that
... such checks are a must for ...
why is the plural subject here followed by "a", a singular determiner?
I read on news that
... such checks are a must for ...
why is the plural subject here followed by "a", a singular determiner?
The short answer: because a must is a fixed idiom.
But we could replace it with a requirement, if the checks are considered collectively: what is required is not each check separately, but the practice of making such checks.
We say “these people are a family” without worrying about the number.