Some of the books appear to be _______ ones that you have read, but after taking _______ second look, you will find that they are different.

A．/; a

B．the; the

C．the; /

D．the; a

贝恩指出的构成进入壁垒的主要因素包括（）.

A.由规模经济所导致的进入壁垒

B.厂商的绝对成本优势

C.产品差别化因素

D.政府的政策法规

E.必要资本量