​The Difference Between the Word Root and the Combining Form

Multiple Choice

​The difference between the word root and the combining form is:

A) ​that a vowel is added to the word root when necessary to make the terms easier to pronounce and more logical
B) ​that a vowel is removed from the word when necessary to make the terms easier to pronounce and more logical
C) ​word root defines whether singular or plural and combining form changes the definition
D) ​all of the above