动词ing形式做主语时,谓语动词要用单数

是的.
Watching basketball games is very interesting.
动词-ing形式做主语有两种格式：
a.置于句首：
例如：Skating on real ice is great fun.
Smoking is bad for your health.
动词-ing形式做主语同时具备名词可以带物主代词的特点也具备动词可以带宾语和状语的特点.
例如：His not coming to school yesterday made the teacher very angry.
b.it 做形式主语,真正的主语放在句末.
例如：
It is no use arguing with him; he won’t change his mind.
It is a waste of time reading such junk mails.
不管哪种形式,记得,动词ing形式做主语时,谓语动词都用单数形式.

一般 是的 假如是并列的二个内容就是复数了

是的 而且必须是用单数