—I like Japanese very much. What about you?
—Not especially. It’s difficult for me _______ .
A:to learn
B:learned
C:learning
D:learn
我国地域广大,且受____气候的影响,由北向南、由东到西,____和____的差别明显,形成了类型众多的生态系统。
在Rt△ABC中,CD是斜边AB中线,且CD=4cm.则AB长为( )