牙的外观叙述，错误的是（）。

A.牙釉质墨氏硬度2度

B.牙骨质覆盖釉质60%

C.牙本质有增龄性变化和反应性变化

D.牙釉质牙尖部最厚约2.5mm

E.牙髓神经只接受痛觉且缺乏定位能力

Many word processing programs include spell checker. It checks the spelling of every word in a (120) by looking up each word in its dictionary. If the word does not appear in the dictionary the user is (121) to possible misspelling and possible corrections are often (122) . Spell checker does not recognize unusual people names or specialized terms, but it will often allow you to create your own personal dictionary of specialized words you often use. Spell checker is a valuable aid to proofreading, but it can not catch the (123) of one correctly spelled word for another (such as form for from). Thus it does not (124) a document is free of spelling errors.

A．alerted

B．alternate

C．guessed

D．guided

E．suggested

F．surprised