胚珠生于花的哪一结构里（）
A.雄蕊
B.雌蕊
C.子房
D.花药
参考答案：B
28. The officer was very concerned ________ the latest development in the case because he was concerned ________ it.
A．about; in
B．for; about
C．with; for
D．in; with
混凝土搅拌时装料数量不应超过搅拌机额定容量的（）。
A.110％
B.120％
C.100％
D.80％
