SVA when subject is a clause starting with what

[aflaamM589]

Dear experts,

Please help me understand that
when a sentence starts with a clause as its subject, verb is always singular as is in following two examples

"What happens in Vegas stays in Vegas."
"What happens in Vegas is gambling and drinking."

But what will be the verb in following kind of sentences

what happen/happens in streets of Vegas stay/stays there.
What happen/happens in Vegas is gambling,dancing,singing and drinking.

Thanks

[RonPurewal]

this kind of thing is very unlikely to be tested. have you seen this distinction actually tested in an official problem?

if you do see this sort of split, go with the singular. but, again, very unlikely.