Which part of Brahman's body are the 'Kshatriya' believed to have been created from, as per Al-Biruni's account?

Shoulders and hands

The correct answer is Option 2: Shoulders and hands

Al-Biruni mentions that the Kshatriya varna is believed to have been created from the shoulders and hands of Brahman.

This is Al-Biruni’s account of the system of varnas: 

The highest caste are the Brahmana, of whom the books of the Hindus tell us that they were created from the head of Brahman. And as the Brahman is only another name for the force called nature, and the head is the highest part of the … body, the Brahmana are the choice part of the whole genus. Therefore the Hindus consider them as the very best of mankind. The next caste are the Kshatriya, who were created, as they say, from the shoulders and hands of Brahman. Their degree is not much below that of the Brahmana. After them follow the Vaishya, who were created from the thigh of Brahman. The Shudra, who were created from his feet . . . Between the latter two classes there is no very great distance. Much, however, as these classes differ from each other, they live together in the same towns and villages, mixed together in the same houses and lodgings