在矩形ABCD中,AB=1,BG、DH分别平分∠ABC、∠ADC,交AD、BC于点G、H.要使四边形BHDG为菱形,则AD的长为____ .
“天苍苍,野茫茫,风吹草低见牛羊”的景观是指( )
—But nowadays children prefer to do things in their own way.