在派对上，主人迎接所有客人是惯例。

It is ___customary for the host to greet all the guests at the party.

青少年之间见面时交换社交媒体账号是常见的。

Among teenagers, it is ___customary to exchange social media handles when they meet.

在许多社会，受邀去别人家时带礼物是习俗。

In many societies, it is ___customary to bring a gift when invited to someone's home.