A:12
B:12 +cosα
C:12 +cosα+cos3α
D:12 +cosα+cos3α+cos5α
赫尔希与蔡斯用32P标记T2噬菌体与无标记的细菌培养液混合,一段时间后经过搅拌、离心得到了上清液和沉淀物。与此有关的叙述不正确的是 ( )
设f(x)=(1+et)x-e2t. 其中x∈R,t为常数;集合M={x|fx﹤0,x∈R},则对任意实常数t,总有( )
俄罗斯的气候特点 ( )
Our charity show for three hours this afternoon. We were tired but very happy.