_____ in the librry regultions thtny book borrowed be returned by due time, or the borrowe

r wil_____ in the librry regultions thtny book borrowed be returned by due time, or the borrower will be fined．Wht is required B．It is required C．s is required D．Which is requiredA．What is requiredB．It is requiredC．As is requireD．Which is required