8-4-2=____
4+1+0=____
7-2-3=____
正常人的卵细胞中的染色体应表示为( )
一 I'm ________ to speak in front of many people.
— Don't worry, John. You can do it.
要证明硬脂酸具有酸性,可采用的正确实验是( )