The old woman is ( ) tired ( ) she can' t walk on.

A. too, to
B. very, that
C. so, that
D. so, to

有271位游客欲乘大、小两种客车旅游，已知大客车有37个座位，小客车有20个座位。为保证每位乘客均有座位，且车上没有空座，则需大客车的辆数是（ ）

A．1辆

B．3辆

C．2辆

D．4辆