Determine the maximum weight of the crate that can be suspended from cables AB, AC, and AD so that the tension developed in any one of the cables does not exceed 260 lb?

i think the answer is a, hope this is right, that would be my best guess.

answer: the correct answer for the fill in the blank is rods.

rods are the specialized photoreceptor cells that are present in the retina of human eye. they are responsible for vision in the night time ( also called scotopic vision). they have very low visual acuity and color distinguishing ability.

as they are responsible for vision in night time, therefore they are found predominantly in the nocturnal animals.