. Many experts agree that once these treasures are _______ to the air, great harm will be done to them. So they think it better not to unearth the treasures.

A．exposed

B．threatened

C．constructed

D．conserved

下列恶性肿瘤中最易发生骨转移的是（）。

A.前列腺癌

B.肝癌

C.甲状腺 * * 状癌

D.肾癌

E.胃癌