Which of the following shows concentration of a solution? * A Grams of solute.
B Liters of the solution.
C Moles of solute per liter solution
D Moles of solvent.​

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.