Do you like skating? ____
It rained for three weeks on end,completely____.(ruin)
氖气是一种稀有气体,若以●表示氖原子,则氖气可用下列( )模型表示
“∵四边形ABCD为矩形,∴四边形ABCD的对角线相等”,补充以上推理的大前提为( )