A and B should be correct
Answer : Half life and radioactive decay are inversely proportional to each other.
Explanation :
The mathematic relationship between the half-life and radioactive decay :
................(1)
where,
N = number of radioactive atoms at time, t
= number of radioactive atoms at the beginning when time is zero
e = Euler's constant = 2.17828
t = time
= decay rate
when
then the number of radioactive decay become half of the initial decay atom i.e
.
Now substituting these conditions in above equation (1), we get

By rearranging the terms, we get

Now taking natural log on both side,

By rearranging the terms, we get

This is the relationship between the half-life and radioactive decay.
Hence, from this we conclude that the Half life and radioactive decay are inversely proportional to each other. That means faster the decay, shorter the half-life.
First equation:
molarity=
no.of moles of solute (Na2S)/volume of solution
0.300/1.75 = 0.171
second equation:
same law
but in volume it is milliliter so you have to convert it by multiplying it with 10^-3
(10 power -3)
to understand it clearly
see this
http://imgur.com/xTS35QM
I believe the answer is solid
Because solid molecules are the most uniform and tight put together molecules
Hope this helps ;)