, I read books at home or travel around the country.          [ ]

A. In my spare time                  

B. On my spare time          

C. At my free time                 

D. For my free time   

目前，诊断肺动脉瓣狭窄首选的无创影像技术是

A．X线平片

B．CT

C．PET

D．MRI

E．超声心动图