超声可以发现最小多少厘米的甲状腺结节（）。

A.甲状腺内所有结节

B.甲状腺内>1.0cm结节

C.甲状腺内<0.5cm结节超声无法显示

D.甲状腺内>0.2cm结节超声均可显示

. Mary was only too ready to help others, seldom, _____, refusing them when they turned to her.

A．if never

B．if not

C．if any

D．if ever