I'm confused on this question.
does anybody know the answer?

The answer is likely B.

Explanation:

I said B, however, the wording is strange. It says "low" solar activity - ...the sun doesn't turn off - but the amount of solar radiation reaching earth can vary. A is eliminated, because there were no cars to consume Fossil fuels during the Pleistocene Age - and the earths orbit did not shift any more particularly that its already tilted axis - eliminating C. The break up of a landmass would not necessarily cause global cooling either. Leaving us with B.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates