Signnatel Inc, ______ world's largest maker of controller chips for MP3 players, is set to establish _______ new R & D centre in Hong Kong and open two sales offices on China's mainland.

A．the; a

B．the; the

C．a; the

D．a; a

下列酶和蛋白因子中，参与DNA复制的是（）。

A．ρ因子

B．σ(sigma)因子

C．DNA结合蛋白

D．释放因子(RF)

E．逆转录酶