严禁使用石块或道钉代替起钉垫，以防滑脱撬棍伤人，压撬棍时不得用力过猛，以免误伤。
参考答案：对
We were shocked to hear the news that ________ two Chinese engineers were shot to death in Pakistan. Worse still, ________ third one died in hospital afterwards.
A．/; a
B．the; the
C．the; a
D．/; the
抗坏血酸呈酸性是因为其结构（）
A.含有烯醇型羟基
B.含有酚羟基
C.含有酯基
D.含有活泼次甲基
E.含有醇羟基
