—What about going abroad for further study?

—Great, but I never expect ______ a chance for me before.

A．there to be

B．there being

C．there is

D．there to have

连结“肺主呼吸”和“心主血脉”的中心环节是

A．经脉的相互连结

B．气血的相互关系

C．心主营，肺主卫之间的相互作用

D．宗气的贯通和运行

E．以上都不是