计算：
（b-2a）2-4a（a-b）。
解：原式=b2-4ab+4a2-4a2+4ab=b2
11. The graduate never expected that his graduation essay would ______ such a heated discussion among scholars.
A．set off
B．set about
C．set out
D．set up
外伤造成的眼球破裂，眼内容大量脱出使眼球变软，摘除中可能的困难有（）、（）。
