切削DN15-DN50mm的圆锥螺纹时，应使用型号的管子铰板（）

A.117

B.114

C.SH－76

D.Q7A－1

A.Q7A-1

B.SH-76

C.114

D.117

A.55°

B.60°

C.45°

D.50°

A.45°

B.50°

C.55°

D.60°

A.45°

B.50°

C.55°

D.60°

A.1/4

B. 1/3

C. 2/3

D. 3/4