sth occurred to me 意思是 我突然想到（记起）什么事的意思.
更常用的结构是it suddenly occured to me that I have left my keys in my room.
“我突然想起我把钥匙落在房间了”
主谓一致中时间金钱度量衡不是说强调数量是用复数:
Five dollars are more than four dollars. 这就在强调数量,数量在这句话里很重要,数量一换句子都不一定对了.
Five dollars is the price of this pencil. 这句话只是把 5 dollars当作一个整体,是铅笔的价钱,不太强调是5块.