Final answer:
In the story 'The Summer of the Beautiful White Horse,' Mourad is believed to be the descendant of the family's 'crazy streak,' characterized by a passionate and adventurous temperament.
Step-by-step explanation:
The question 'Who is believed to be the descendant of the crazy streak?' pertains to the characters in the story 'The Summer of the Beautiful White Horse' by William Saroyan. The answer to this question is b) Mourad, who is described as having inherited the family's crazy streak. The streak is referenced as a positive trait of being passionate and adventurous, rather than literally being insane. In the context of the story, this familial trait is best embodied by Mourad, who is the main character Aram's cousin and is known for his spirited and somewhat impulsive actions, like 'borrowing' a horse.