慢速英语:'Tornado Season' Begins in the United States

音频下载[点击右键另存为]

not necessarily未必，不一定

例句：Freedom does not necessarily imply responsibility.
      自由不一定包含着责任。

2.But no matter what the size, tornado winds are the strongest on Earth.

no matter what无论如何, 不管怎样

例句：He's decided to leave tomorrow, no matter what.
      不管发生什么事, 他已决定明天走。

      I'll always love you, no matter what.
      不论出什么事, 我永远爱你。

3.On average, eight hundred tornadoes are reported nationwide each year.

on average平均，按平均数计算

例句：On average, there were 200 deaths each month.
      一般说来，每月有200人死亡。