18,-27,36,( ),54
A.45
B.44
C.-45
D.-44
参考答案:C
It is my first time _________ fireworks. How beautiful! [ ]
A. see
B. sees
C. seeing
D. to see
含巯基的氨基酸是()
A.半胱氨酸
B.丙氨酸
C.亮氨酸
D.组氨酸