牙列缺失是临床的一种常见病、多发病,多见于________。
“En-” in “enrich” is a(n) ________________.
A. derivational affix
B. inflectional affix
C. free root
D. bound root
The base form of a word that cannot further be analyzed without total loss of identity is called a___________.
A. root
B. stem
C. morpheme
D. affix