As a woman volunteer, she is keen on uniforms.()
查看答案
组成人体的必需氨基酸是
A. 丙氨酸
B. 甘氨酸
C. 瓜氨酸
D. 色氨酸
E. 半胱氨酸
Most of the environmental problems are man-made.()
Santa has got to Billy's house already .()
The train arrives at the North Pole at five to the midnight.()