There is a new problem       the popularity of private cars that road conditions need       .  [ ]

A.involved in;to be improved

B.involving in;to be improved

C.involving in;improving

D.involved in;improved

诊断胆囊结石首选的检查方法是（）

A.腹部X线平片

B.B超

C.口服胆囊造影剂

D.CT

E.MRI