For which of the following prostheses would biocompatibility not be a serious issue?
A. A hearing aid
B. Contact lenses
C. An engineered arm connected to nerve endings so that it can
respond to brain signals
D. A heart valve

a hearing aid.

it doesn't get in contact with fluids (like contact lenses) and doesn't get implanted, so it got not much to do with the immune system

the answer is either b or c

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: