What is the reason?

When building a custom page we need to get a collection of data. To determine how many items are in this collection, the Adobe Commerce developer uses $collection->count() . This sometimes is slow and causes some delay.

What is the reason?
A . The collection is loaded first and then the number of items in the collection are returned.
B . Before the collection is loaded, the framework performs left joins for all related attributes
are added to the query.
C . The framework internally uses SELECT count(-) and that is slower than loading the collection.

Answer: B