Final answer:
The subject of this question is History and the grade level is High School. The question asks about the Indus Valley Civilization, also known as Civilization X, and its associated languages.
Step-by-step explanation:
Civilization X refers to the Indus Valley Civilization, which was an ancient civilization that thrived in the Indus River Valley in what is now modern-day Pakistan and northwest India. It is also known as the Harappan Civilization.
The Indus Valley Civilization was a highly advanced society that developed around 2600 BCE and lasted until 1900 BCE. It had well-planned cities, advanced infrastructure, a system of writing, and traded with other regions.
This topic falls under the subject of History and is typically covered in high school World History courses.