The early Namgyal rulers faced challenges from:

The correct answer is: d) All of the above.

The early Namgyal rulers faced challenges from neighboring kingdoms like Nepal and Bhutan, internal power struggles, and natural disasters.

• Neighboring kingdoms like Nepal and Bhutan were constantly trying to expand their territory, and the Namgyal rulers had to defend their kingdom from attack.
• Internal power struggles were also common, as different factions within the Namgyal family vied for control of the kingdom.
• Natural disasters, such as earthquakes and floods, also caused great damage to the kingdom and its people.

Despite all of these challenges, the early Namgyal rulers were able to maintain the independence of their kingdom and lay the foundations for the modern state of Bhutan.