如未按常规程序进行塑料热处理操作，结果义齿基托会出现"花基板"，且发生变形，密合度差。

常规热处理方法是 （）

A.100℃恒温2h

B.70℃恒温24h

C.60℃恒温12h

D.120℃恒温20min

E.70℃恒温1.5h，100℃恒温1h

--- Do you mind telling us something about this area?

--- Not at all. ________ of the land in this area _________ covered with trees and grass.

A．Two fifth, is

B．Two fifth, are

C．Two fifths, is

D．Two fifths, are