The ambitious project to improve road connectivity across Arunachal Pradesh is known as the:

Trans-Arunachal Highway
Bharatmala Pariyojana
Pradhan Mantri Gram Sadak Yojana
Arunachal Pradesh State Highway Development Project

The correct answer is: a) Trans-Arunachal Highway.

The Trans-Arunachal Highway is a highway project in India that aims to connect all the 27 districts of Arunachal Pradesh by road. The highway is being built in phases, and the first phase was completed in 2018. The second phase is currently under construction, and the third phase is expected to be completed by 2022.

The Trans-Arunachal Highway is a major infrastructure project that will have a significant impact on the development of Arunachal Pradesh. The highway will improve connectivity between the different parts of the state, and it will also boost economic activity. The highway will also make it easier for tourists to visit Arunachal Pradesh, which is a beautiful and scenic state with a rich culture and history.

The other options are incorrect because they are not related to the Trans-Arunachal Highway. Bharatmala Pariyojana is a highway project that aims to improve road connectivity across India. Pradhan Mantri Gram Sadak Yojana is a rural road development project. Arunachal Pradesh State Highway Development Project is a state government project that aims to improve road connectivity in Arunachal Pradesh.