C. 3.10 g, 3.20 g, 3.23 g
I came to this conclusion because:
A. 3 g, 4 g, 5 g, well these have 10 units between (0.1, .2, etc) so they are not the closest.
B. 3.0, 4.0, 5.0 just like above, they still have 10 units between
D. 3.0, 4.0, 5.0, 6.0 these numbers, just like in the previous two, have 10 units between, making them not precise or the closest option.
C is your answer because 3.10 - 3.23 are only 2 units apart. Making them the most precise.