圆周长C与圆的半径r之间的关系为C=2πr,其中变量是____ ,常量是____ .
Many of the things we now benefit from would not be around _______ Thomas Edison.
西汉前期,统治者实行休养生息的政策,出现的盛世时期被称为( )
数:shù____ shǔ____
中:zhōng____ zhòng____