Assertion: The Indus Valley civilization is also called the Harappan civilization.
Reason: The Indus Valley civilization was named Harappa after a famous ruler.

The Assertion is correct but the Reason is incorrect.

The correct answer is Option 4  -The Assertion is correct but the Reason is incorrect.

Assertion: The Indus Valley civilization is also called the Harappan civilization. (correct)
Reason: The Indus Valley civilization was named Harappa after a famous ruler. (incorrect)

The Indus Valley Civilization or the Harappan culture derives its name from Harappa, the first site where this distinctive culture was unearthed.
The civilization is dated between approximately 2600 BCE and 1900 BCE.
Alongside the Harappan culture, there were earlier and later cultures in the same area known as Early Harappan and Late Harappan respectively.
The term "Mature Harappan culture" is sometimes used to differentiate the Harappan civilization from these earlier and later cultures.