31. Which materials would most likely be used by designers of ornithopters to mimic the bone structures of pterosaur wings? A. heavy metals to prevent bends and tears in the wings B. wooden replicas of bones to create identical structures for the devices C. lightweight metals and open-space structures for the wings D. plastic replicas of bones that have a completely filled-in structure

the answer would most likely be c, because if it's a comical piece of information, it may likely not be true, if it's a site that allows anybody to edit the content, it could mean a five year old is typing the info, and if it's a tv show produced by a celeb, it may have a biased opinion.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray