Answer:
The last option 15,000 grams is correct.
Explanation:
How many grams are in 15 kilograms? 
We must know the relation between kilograms and grams.
1 kg = 1000 grams.
Now we have been asked to calculate the grams in 15 kilograms.
So, 15 kilograms has = 
 grams
Therefore, the last option 15,000 grams is correct.