I received an offer from a top US engineering Ph.D. Program. Let's say this is Program A. I also have another offer program B. Currently, I am waiting on program C's decisions. The potential advisor from C is very positive he will have full funding + offer for me soon. All A, B, and C are my TOP choices and TOP engineering Ph.D. programs in the U.S.
My preference is as follows with a 'confidence value of my preference' estimated in brackets. A_offered (0.90) > C_waiting (0.87) > B_offered (0.83)
My dilemma is that the advisor from A emailed me that they want to know my decision a couple of weeks before the 04/15 deadline. An official offer letter was attached to that email.
Though I am leaning toward program A, I am still looking into program B and waiting on program C's offer.
Would it be okay to respectfully ask the advisor from A that I will need more time to make my decision?
And, if I do ask him for more time, is there a possibility that he will rescind my official offer?