用氧-乙炔割炬切割金属时，（）。
A.先开乙炔点燃后，再开氧气
B.先开氧气，后开乙炔
C.同时打开氧气乙炔
D.先开乙炔，后开氧气，然后点火
参考答案：A
具有CD3分子表面抗原的是（）。
A.Mφ
B.T细胞
C.B细胞
D.NK细胞
E.嗜碱性粒细胞
The project life-cycle can be described as（）
A.project concept, project planning, project execution, and project close-out
B.project planning, work authorization, and project reporting
C.project planning, project control, project definition, WBS development, and project termination
D.project concept, project execution, and project reporting
