—Liu Qian is good at doing the tricks with the cards.

—Yes, but if you watch carefully, you can see _______he does them.

A．who

B．what

C．which

D．how

关于球后溃疡病临床表现下列哪项是不正确的( )

A．夜间痛、空腹痛较多见

B．一般发生在十二指肠水平部

C．疼痛常向背部放射

D．大量出血多见

E．内科治疗效果较差