The mighty empire whose territories encompassed Haryana during the 4th and 5th centuries CE was the:

The correct answer is the Gupta Empire.

The Gupta Empire was an Indian empire that ruled over much of the Indian subcontinent from the mid-4th to late 6th centuries. It was founded by Chandragupta I in 320 CE and reached its zenith under the reign of his grandson, Samudragupta (335–375 CE). The Gupta Empire was a golden age for Indian culture, science, and technology. It was during this time that the Sanskrit language and literature flourished, and that many important mathematical and scientific discoveries were made. The Gupta Empire also saw the construction of many impressive temples and palaces.

The Kushana Empire was an empire that ruled over much of Central Asia and the Indian subcontinent from the 1st to 3rd centuries CE. It was founded by Kujula Kadphises in the 1st century CE and reached its zenith under the reign of Kanishka I (c. 127–150 CE). The Kushana Empire was a major power in the region, and its rulers were patrons of Buddhism.

The Maurya Empire was an Indian empire that ruled over much of the Indian subcontinent from the 4th to 2nd centuries BCE. It was founded by Chandragupta Maurya in 321 BCE and reached its zenith under the reign of his grandson, Ashoka the Great (272–232 BCE). The Maurya Empire was a major power in the region, and its rulers were patrons of Buddhism.

Harsha’s Empire was an Indian empire that ruled over much of the Indian subcontinent from the 7th to 8th centuries CE. It was founded by Harshavardhana in 606 CE and reached its zenith under his reign. Harsha’s Empire was a major power in the region, and its ruler was a patron of art, literature, and religion.