They are all correct. It depends what information you want to give us about time. Does it happen regularly? - lays Did it happen in the past? - laid Is it happening now? - is laying Which one do you want to say?

yes, thank you. :)

There has to be a tense!! Tense is not optional. :)))) You can use any tense you like but there has to be a tense. Each tense fits the sentence.

what if there is no specific tense used in the sentence just like in My mother(lays/laid/is laying)my baby in his crib? can i use any verb in any tense i like?

It depends on which tense you want to write the sentence in. Past, present or future?