The species formed when a proton is removed from an acid is called the a. antacid. b. buffer c. conjugate acid. d. conjugate base. e. cation

d. conjugate base.

Explanation:

Conjugate base -

As , a proton is removed from an acid , it lead to the formation of a conjugate base .

For example ,

Consider an acid HA , the proton is lost from the acid in the following way -

HA >  H⁺   +    A⁻  

H⁺  is the proton lost

And ,

A⁻  is the conjugate base .

Hence , from the given option of the statement , the correct term is  d. conjugate base .