are is peter做否定回答,not

关于are is的用法
Everything including roofs ,trees and grass was covered with snow.请问这句话中为什么是was 而不是were

选词填空
there[ ]a window,acomputer and a desk.[are is]
there[ ]two bedrooms,aliving room,a bathroom and alitchen.[are is]
[ ]there a river in the park?[are ls]
[ ]there any birds in the sky?[are ls]
the panda[ ]climd=b the trees.[can can;t]
what's it[ there is a bad and a desk.[like /]