—Yes, at _______ it's _______ the one you bought for me.
A：last; as bad as
B：least; no better than
C：last; not better
D：least; no worse than
若A(a，b)，B(b，a)表示同一点，那么这一点在 ( )
则：
平均命中环数为____；命中环数的方差为____．
