The house rent is high, I've got about half of the space I had at home and I'm going to pay ______here.

A．as four times much

B．as much three times

C．much as three times

D．three times as much

受抗原第一次刺激，机体首先产生的特异性抗体是

A．IgG

B．IgM

C．IgA

D．IgE

E．IgD