"Choosing appropriate architectures" - singular or plural agreement?

Choosing appropriate architectures {are} crucial

or

Choosing appropriate architectures {is} crucial

To my knowledge [choosing something] is a single action, it should be followed by [is]. Please correct me if it is wrong and will be great if you come up with a little explanation...!

Thanks in Advance.


The subject of your sentence is choosing appropriate architectures, which has singular agreement. The subject is choosing, not architectures.

The sentence should read:

Choosing appropriate architectures is crucial.