More than two thirds of the land of the expo garden ________ with trees and grass in the past few years.
从西周“普天之下,莫非王土”到战国商鞅“废井田,开阡陌”,直接反映了( )
读出下面游标卡尺和螺旋测微器的读数.
①____mm; ②____cm.
如图电路,若要使灯L1、L2串联,则应闭合的开关是____ ;若要使灯L1、L2并联则应闭合的开关是____ 。