What is special about Mr. Phelps’s degree

A．It integrates an assortment of courses.

B．It includes Economics in the curriculum.

C．Courses are taught individually.

D．Students learn in separate booths.

龋病过程中无下述哪项()

A．硬组织崩解

B．硬组织再生

C．色素沉着

D．软化牙本质存在

E．上述四项都存在