Which Is Generally NOT True of Differentiation

Short Answer

Which is generally NOT true of differentiation?
a. Difficult to sustain basis of differentiation in the long run.
b. Relentless efforts of competitors to duplicate differentiation.
c. Key areas of application include research and development, marketing/sales and after-sale services.
d. It is a challenge to identify attributes that are valued by customers in each market segment.
e. Inability to pass on suppliers' price increases to buyers.