1.after-sale 售后服务

例句：We have some questions about after-sale services.
我们对售后服务有几点疑问Jf8Wdw(W,D-WM=JvAq#。

2.specialize in 专门

例句：Many students specialize in engineering.
许多学生专攻工程学5*w0,wljqvXfIiJ9r;。

3.come under 受到

例句：The police came under attack from angry crowds.
警察遭到愤怒的人群的袭击fy.,@_3CmgL=1274V。

4.a group of 一群

例句：But a group of six women and 23 children got separated from the others.
但是有一群人和其他人走散了，其中有6名妇人和23个孩子RN&~-Zq)[f^-+t。