-To find significant figures, you always start by counting the FIRST NON-ZERO DIGIT in the number.
-Non-Zero digits are ALWAYS significant figures
A is a whole number, and has no decimal points, so you would count the first and last non-zero digits (5 and 2). If there were any zeros in between these numbers (eg. 302) we would also count them, but since all the zeros are BEHIND the last non zero digit (2) we DON'T count them. This leaves only two significant figures.
B, C, and D are all decimals, so the rules for counting are slightly different. Again, you start by counting the FIRST non zero digit, even if it is after the decimal (like in D) and you finish counting at the LAST digit in the number, even if it is a zero.
B, we would count 8, 0, 0, 2. This is only 4 significant figures.
D, we would count 2, 3, 5, 0. It doesn't matter that the 2 is behind the decimal, since all non-zero numbers are significant figures. The 0 at the end also counts because it is the last digit in the number. This is still only 4 significant figures.
This leaves only C! C, we would count 6, 0, 0, 0, 0. 6 is the first non-zero digit, and since it is a decimal we go all the way to the last digit, aka 0. This counts 5 significant figures.
In summary, gravity is the force that creates the pressure to fuse atoms, which makes the stars shine. Eventually the temperature is high enough that the star starts fusing hydrogen into helium. When the outward pressure produced by the heating of the gas by fusion energy balances gravity, a stable star is formed.
The density of the liquid is less than that of water. If the density of the liquid is less than that of water, it will float in it. Hence, if you pour some of the liquid into a glass of water, it will float.
