以下β受体阻断药物中具有内在拟交感活性的药物是

A．普萘洛尔

B．吲哚洛尔

C．噻吗洛尔

D．阿替洛尔

E．美托洛尔

—How unhappy your roommate looks!

—Yes, but he's not willing to tell me what it is _______ is troubling him.

A．what

B．which

C．as

D．that