Each of the Following Groups of Things Has Been Divided

Multiple Choice

Each of the following groups of things has been divided according to a single basis of classification. However, one item in each group does not belong; it does not fit that single basis of classification. Read each group of items carefully; then, select the letter of the one item that does not belong.
-Types of pain

A) sharp, shooting pain
B) burning pain
C) aching pain
D) constant pain