A = false, it will take 0.031 cal to raise 1g Au 1degree while it will take 0.033 cal to raise 1g Hg 1 degree so, although Au will heat up faster, it will not be discernably faster so...
b = true
c = false, Au density > Hg
d = true
One of the major limitations of using the ball and stick model for DNA, is that within a single double stranded segment of DNA, one would have to use many many balls to represent atoms that are present in the sugar phosphate backbone, along with all of the main atoms that compose the nitrogenous bases of DNA, we also cannot construct or show the helical form of DNA, by using balls and sticks as well.
density = mass/volume = 100kg/10ml = 10kg/ml
voluime = mass/density = 50g/2 g/ml = 25 ml
mass = density x volume = 2x55 = 110 kg
Do you not understand how to solve for the answer?