a number of 意思是“许多...”,后接复数名词,谓语通常用复数：
A number of students were absent from the meeting.
许多学生没有到会.
可加不可数名词可以举个加不可数名词的句子吗？A number of water pollution sources exist in the upstream of Shahe reservoir in Tianmu Lake tourism resort.天目湖旅游度假区沙河水库上游存在多种水体污染来源，这些污染物质可通过雨水径流进入库区。