一元二次方程x2-4x-6=0，经过配方可变形为 [ ]
A．(x-2)2=10
B．(x-2)2=6
C．(x-4)2=6
D．(x-2)2=2
答案：A
______, most of the spelling mistakes can be avoided.
A．Checking your composition carefully
B．Check your composition carefully
C．If you check your composition carefully
D．Your composition is carefully checked
