A.a great inventor
B.was a great inventor
C.a great inventor who
D.who, as a great inventor
A.will graduate
B.am graduating
C.have graduated
D.will have graduated
A.had not allowed, would not have
B.had not allowed, would not have had
C.didn't allow, would not have
D.didn't allow, would not have had
A.should never lose
B.can never lose
C.should never have lost
D.would never have lost