患者男性，25岁，左下腹痛伴脓血便半个月。查体腹部无异常，首先选用的检查方法是

A．大便常规菌培养

B．B超

C．钡剂灌肠透视

D．全胃肠钡剂检查

E．全结肠镜检查

The old man              in front of the door, waiting for his children to come back home.[ ]

A．was used to sit

B．is used to sit

C．used to sit

D．used to sitting