急because of加句子与because加句子的区别

比方说:因为我病了,所以不能去上学
I can't go to school today,because I am ill.
I can't go to school today,because of my illness.
所以应该前者跟句子,后者跟名词性的短语.
because of加名词或动词ing、because加句子、填because 吧