All of the following statements concerning buffers are true EXCEPT:
a. Buffers are resistant to changes in pH upon the addition of strong acids.
b. Buffers are resistant to changes in pH when diluted with water.
c. The pH of a buffer is close to the pKa of the weak acid from which it is made.
d. Buffers contain appreciable quantities of a weak acid and its conjugate base.
e. Buffers are used as colored indicators in acid-base titrations.