A:π键是由两个p电子“头碰头”重叠形成的
B:σ键是镜像对称,而π键是轴对称
C:乙烷分子中的共价键全为σ键,而乙烯分子中含有σ键和π键
D:H2分子中含有σ键,而Cl2分子中除σ键外还含有π键
在输入语句中,若同时输入多个变量,则变量之间的分隔符号是( )
阅读下面短文,将文中划线句子译成中文。 Some kids in boarding school often like to talk with their roommates. ____ They won’t stop talking until someone comes to stop them. This is the reason why many of them are sleepy in class the next day. Lack of (缺乏) sleep is bad for their health. Growth hormones (生长激素) are very important if one is to grow taller. ____ The body makes the most hormones between 10 p.m. and 2 a.m. While you are asleep. ____ This means that if you don’t get to sleep at the time, you won’t grow taller.
____的糖槭是最有名的木本糖源。