______ you have got an MA degree,you are qualified for a PhD program.

because是从属连词,接表示直接原因的从句,一般放在主句的后面,也可放在主句前面,它表示的语气最强,在回答why的问句时,必须用because.
实际上,不是因为有MA degree,就一定是qualified的.因此,说话者是根据一般事实作出的推断,用since自然更好.
例如：The swimming pool won't be open today because they're making repairs.
游泳池今天不开放,因为他们在修理.
Why did you move to France?
你们为什么搬到法国?
Because my father found work in Paris.
因为我父亲在巴黎找到了工作.
注意：在英语中用了because后,不可再用so.
since 意为"既然",表示对方已知的无需加以说明的原因或事实,语气比because弱,但是比as 强.
例如：Since we have no money,we can't buy that vase.
既然我们没钱,我们就不能买那花瓶.
Since everybody is here,let's begin our party.
既然大家都到了,那就开始我们的聚会吧!