The correct option is C The most important/significant evidence of the achievements of this civilization have been excavated from Harappa.
Indus Valley Civilization which is also referred as Harappan civilization is of the largest cities of its time.This civilization was discovered in 1920 - 22 with the excavation of two of its most important sites i.e , Harappa on the banks of the river Ravi and Mohenjodaro on the banks of the Indus. The Indus Valley civilization is called the Harappan civilization because Harappa was the first site where the unique archaeological evidences of the civilization were discovered.