若双链DNA分子的一条链的A:T:C:G=1:4:3:6,那么其另一条链上同样的碱基比为[ ]
A.4:1:6:3
B.1:4:3:6
C.6:4:1:3
D.3:1:6:4
答案:A
制作一个底面半径是50厘米,长是200厘米的圆柱体的通风管,至少要用多少平方厘米的铁皮?
We went to Professor Li’s yesterday. He gave us________. [ ]
A. some advice
B. advices
C. an advices
D. some advices