clause (who, that, which, where). e.g. My mom is the doctor. She treats my friends. -> My mom is the doctor who treats my friends. There are two towns near here. They have railway stations.

Ответ

В первом предложении нужно использовать слово who, так как оно относится к человеку (doctor):

My mom is the doctor who treats my friends.

Во втором предложении нужно использовать слово where, так как речь идет о месте (towns):

There are two towns near here where they have railway stations.