SALT question for a preschooler

[Bambalina]

I feel like I should know this, but when did your children start understanding and responding appropriately to "why/what/who?" questions?

Miss 3, I feel, has been a late talker - I've been watching closely wondering if and when to get SaLT involved. Her expressive language has really taken off over the last 6 months and makes herself understood as I would expect for that age. But if I ask her something like "what is it?" "why did X happen" or some other such abstract term, she either doesn't reply, or just replies "yes". Which leads me to believe that concretely/contextually she is all well and good, but when does the abstract comprehension actually start to kick in?

[VioletBam]

Both of my DDs could answer what/where/why/who questions at three. One was a very early and articulate speaker and the other average.

I would seek help now OP if she's not responding to these questions at this point.