A:①④
B:②③
C:③④
D:①②
Little Tom was frozen with fear when the accident happened, so he just gave some ________ answers when asked about what he witnessed.
1969年,人们发现坠落在澳大利亚启逊镇的陨石中含有并非来自地球的氨基酸(构成生物体所需的有机物之一),由此可推测( )
性染色体为(a)XY和(b)YY之精子是如何产生的( )
—____ coat do you like, the red one ____ the green one?
— I like this____one.