钢结构柱绑扎时，应首先明确其重心位置，吊点必须位于其重心之上。
参考答案：对
下列哪种氨基酸为嘌呤和嘧啶核苷酸生物合成的共同原料（）。
A.谷氨酸
B.甘氨酸
C.天冬氨酸
D.丙氨酸
E.天冬酰胺
Questions 27～30
A. The man has always been a valuable employee. B. The man has often been late for work after lunch. C. The man has been addicted to alcohol while running errands. D. The man has been engaging in work-related activities.
