The correct answer is: B. Samudragupta
Samudragupta was the third ruler of the Gupta Empire. He was the son of Chandragupta I and Kumaradevi. Samudragupta ascended the throne in 335 CE and ruled for 40 years. He was a great conqueror and expanded the Gupta Empire to its greatest extent. He annexed all the Janapadas of Himachal Pradesh.
Chandragupta Maurya was the founder of the Mauryan Empire. He ruled from 321 to 297 BCE. He was a great conqueror and expanded the Mauryan Empire to include most of the Indian subcontinent. However, he did not annex the Janapadas of Himachal Pradesh.
Asoka was the grandson of Chandragupta Maurya. He ruled from 272 to 232 BCE. He was a great emperor and a Buddhist reformer. He is known for his non-violent policies and his promotion of Buddhism. However, he did not annex the Janapadas of Himachal Pradesh.
Chandragupta-II was the grandson of Samudragupta. He ruled from 375 to 415 CE. He was a great conqueror and expanded the Gupta Empire to its greatest extent. However, he did not annex the Janapadas of Himachal Pradesh.
The Janapadas of Himachal Pradesh were a group of small kingdoms that existed in the region before the Gupta Empire. They were eventually annexed by Samudragupta.