The statement that best compares the source of ethnic tensions in Myanmar and Cambodia is:
Myanmar is a Buddhist country and the Rohingya minority are Muslim and in Cambodia, the Vietnamese are Buddhist and the Cambodians are Muslim.
However, it's important to note that in Cambodia, the majority group (Khmer) is predominantly Buddhist, and while there are tensions with the Vietnamese, both groups primarily practice Buddhism. The key point of comparison here is the Buddhist-Muslim divide in Myanmar, particularly with the Rohingya, who face significant persecution. The tensions in Cambodia generally relate more to national identity and migration rather than religious differences.