A major hydropower project that has faced some environmental concerns in Arunachal Pradesh is the:

Kameng Hydroelectric Project
Dibang Multipurpose Project
Subansiri Lower Hydroelectric Project
Teesta Hydroelectric Project

The correct answer is: c) Subansiri Lower Hydroelectric Project.

The Subansiri Lower Hydroelectric Project is a proposed 2,000 MW hydroelectric project on the Subansiri River in Arunachal Pradesh, India. The project has been facing environmental concerns since its inception, and has been opposed by local communities and environmental groups. The project is currently on hold due to these concerns.

The Kameng Hydroelectric Project is a 2,000 MW hydroelectric project on the Kameng River in Arunachal Pradesh, India. The project was completed in 2003 and is currently operational.

The Dibang Multipurpose Project is a 2,880 MW hydroelectric project on the Dibang River in Arunachal Pradesh, India. The project is currently under construction and is expected to be completed in 2023.

The Teesta Hydroelectric Project is a 3,000 MW hydroelectric project on the Teesta River in Sikkim and West Bengal, India. The project was completed in 2006 and is currently operational.

The Subansiri Lower Hydroelectric Project is the only project among the four that has faced environmental concerns. The project is located in a sensitive area with a high biodiversity. The project is also likely to have a significant impact on the downstream riverine ecosystem. The project has been opposed by local communities and environmental groups, who have raised concerns about the project’s impact on the environment and the livelihoods of the people living in the area. The project is currently on hold due to these concerns.