B, a physical change because it is not destroying the substance.
Anything that occupies space and has mass.
If you go by the decimal there should be 5 significant digits because 0 is a trailing zero and matters since it comes after a decimal. however if you do
6.3590 x 10 ^7 = 63590000 then you would only have 4 significant digits because there is no longer a decimal to make the zero after the 9, significant.
Hope this helps!
I believe a. is the answer.
