(2013·咸阳二模)—Have you seen ________ pen？I left it here this morning.

—Is it ________ black one？I found it in the corner.

A．a；the

B．the；the

C．a；a

D．the；a

壁厚为5~10mm的黄铜管焊前预热温度为()℃。

A.100~200

B.200~300

C.400~500

D.500~600