專業為英語怎麼翻譯

『壹』 「專業」用英語怎麼說

major;
specialty;
profession;
例句：
1 So are you the professional guitar player?你就是來那個自專業的吉他手嗎？
2 What was your major? 你的專業是什麼？
3 But he refused those professional actors.
但他拒絕了那些專業演員.