Putting an index finger up to the lips is a popular way _____ Be quietto sayfor saying of saying of say
问题描述：
Putting an index finger up to the lips is a popular way _____ Be quiet
to say
for saying
of saying
of say
答
可是我认为填saying就得了，我认为它其实就是省略了：a popular way that/which is saying
答
of saying
答
of saying
以下供参考：
American ways of living
美国人的生活方式
答
Putting a index finger up to the lips is a popular way to say Be quiet.