下列高分子材料中，主要作肠溶衣的是
A．羟丙甲纤维素
B．甲基纤维素
C．丙烯酸树脂Ⅱ
D．聚乙二醇
E．川蜡
参考答案：C
—What has made him upset recently?
—____alone to face a troublesome milk case.
A．Left
B．Being left
C．Having left
D．To leave
如何有效的进行战略联盟？
