问题

How old is your grandpa this year , Tom — ___________. And we are planning a party for his ________ birthday.
A:ninety ; ninety
B:ninetieth ; ninetieth
C:ninety ; ninetieth
D:ninety ; ninetieth;
B:ninetieth ; ninetieth
C:ninety ; ninetieth
D:ninety ; ninetieth;
正确答案是: