芽接苗剪截砧木，一般树种苗在接芽上部（）剪截。
A.1～3cm
B.2～5cm
C.3～7cm
D.5～10cm
参考答案：D
—Don't _____ our hopes. Things will be fine soon.
—Yes. We should learn to be brave when we are in difficulties. [ ]
A. cheer up
B. give up
C. clean up
D. turn up
每个肝小叶中央都贯穿一条（）。
