The answer is B. Light microscope
I think you b and c is the other way around.
Regardless, the answer is Two elephants
The air pressure on your body is about 10kg same as the weight of 2 elephants
Displacement is usually the method that is used to measure the volume of a solid with an irregular shape
The answer would be A packing becomes less tight. The double bounds create kinks in the chain making it harder for the chains to back tightly