Questions sometimes arise about the deadline for replying to offers. There is a pretty firm April 15 deadline for most American schools. You can read the policy at
https://cgsnet.org/ckfinder/userfiles/files/CGS_April15_Resolution_Oct2020Revision.pdf
and read the FAQ at https://cgsnet.org/ckfinder/userfiles/files/2020%20April%2015%20Resolution%20FAQ%209_2020.pdf