英语选择,It's rained heavily this morning,but______of my classmates were away from school.用all还是用none,怎么根据句意判断啊

英语选择,
It's rained heavily this morning,but______of my classmates were away from school.
用all还是用none,怎么根据句意判断啊

all
如果是none,后面的were应该是was