解释下列词语
①莫名其妙
②苦心孤诣
①没有人能说明它的奥妙(道理),表示事情很奇怪,使人不明白。②指苦心钻研,独有创见。
_______girl was ill.( )
This kind of sweater is too ____. I want to buy a cheap one.