破伤风引起病人一系列临床症状和体征的主要因素是

A．痉挛毒素

B．内毒素

C．溶血毒素

D．破伤风杆菌

E．破伤风杆菌的芽孢

So far as English is concerned,it is not______ you might think.

A．so difficult

B．so difficult as

C．so much difficult

D．so difficult that