Final answer:
The given statement "According to Prothero, the Sanskrit language and the importance of horses militates against an Indus Valley origin of Hinduism and in favor of an Aryan source." is true. The statement that Sanskrit and the significance of horses indicate an Aryan rather than an Indus Valley origin of Hinduism is true, according to Prothero's theories supported by historical evidence. So, the best answer is a, true.
Step-by-step explanation:
According to the theories and evidence put forth by scholars like Prothero, the assertion is true that the Sanskrit language and the importance of horses militate against an Indus Valley origin of Hinduism and in favor of an Aryan source.
The Sanskrit-speaking Aryans, who were nomadic pastoralists that valued horses highly, are said to have migrated from the Eurasian Steppe around 3500 BCE and spread into regions including India.
The practice of horse sacrifice, ashvamedha, was a significant ritual among the Aryans and marked the king's right to rule over the lands traversed by the horse.
This ritual, along with linguistic evidence, suggests that the Aryans were not native to the Indus Valley but instead brought their culture, language, and religious practices from regions to the northwest.
So, the best answer is a, true.