Tom is always ready ____ (help) others. All of us should learn from him.
比一比,再组词。
鲸 ____
掠 ____
设F为抛物线C:y2=4x的焦点,曲线y= kx (k>0)与C交于点P,PF⊥x轴,则k=( )
人们为了提高家蚕的吐丝量,往往会在桑叶上喷洒一种化学物质给蚕食用。这种化学物质应在蚕发育的哪个时期喷洒 ( )
We are sure ________ the football match.
____
(从上到下依次填写)