下面哪一组字母的顺序是正确的。

Though having lived abroad for years, many Chinese still ____ the traditional customs.

It is uncertain ___ side effects these weight-loss drugs will bring about, although hundreds of thousands of patients have taken it

Lucy and Sam made an appointment of an interview on Sunday afternoon,________ they would be free.

______ the help of the teacher, the student who wasn’t good at math ______ the difficult problem quickly