水泥粉煤灰碎石桩的桩土形成的复合地基，其承载力提高幅度可达()倍以上。
A.2
B.3
C.4
D.5
参考答案：C
Th细胞活化所需的IL-2是由下列哪种细胞分泌的（）
A.APC细胞
B.B淋巴细胞
C.Th细胞
D.CTL
E.Ts细胞
Though he came out ___________ in the 100-meter dash, he was made __________ second
best player in the sports meet held on ___________.
A．the first; a; April 22nd
B．first; the; May 31th
C．first; the; May 31st
D．the first; /; April 23rd
