Asubstance has half the number of particles as 12 grams of carbon 12, how many moles are in the substance?
a. 1.0
b. 1.5
c. 2.0
d. 0.5

the molar mass is how many grams it takes to make a full mole.  The number  in carbon 12 tells us that it takes 12 g to makes a mole, so one half of that would be option d, 0.5.  

d. 0.5

Explanation:

A mole is the amount of matter that is present in a certain substance and it is compared or measured against the amount of particles that can be found in 12 grams of Carbon 12, which is the most common isotope of Carbon that can be found in nature, so if a substance has half of the particles as 12 grams of Carbon 12, that means that it is only half a mole, so there are .5 moles of the substance.