The moonlight is coming in --- the window and the room seems

The moonlight is coming in ___ the window and the room seems quiet and beautiful.
A.across B.though C.over D.by
请尽快解答并说明原因,
答案：B through
从某一物体内部穿过用through.
再问： 恩...不太明白这句子的意思。请帮忙翻译下好吗？
再答： 月光穿过窗户玻璃照射了进来，房间好像非常的安静和美丽。