Final answer:
The question asks how many necklaces have jade, but without the number or proportion of necklaces with other gemstones, we cannot determine the answer. The necessary information to calculate the answer is missing.Since that part of the question is missing, we cannot definitively answer which option (a, b, c, d) is correct.
Step-by-step explanation:
Jennifer sells gemstone necklaces and has a total of 42 different necklaces.
The question does not specify the exact proportion or number of necklaces with rubies, emeralds, and sapphires.
Therefore, we cannot determine the number of each type of gemstone necklace.
However, we are given that the remaining necklaces have jade.
To find out how many necklaces have jade, we need to know the numbers for the other gemstones or their proportions.
Since that part of the question is missing, we cannot definitively answer which option (a, b, c, d) is correct.