Answer:
Option C, needles
Step-by-step explanation:
In a cactus plant, pointed thorn like leaves also called as needles are found. if we compare a chromosome with a cactus plant, then the genes can be compared to the needles. As needles are found on cactus plant, genes are found on chromosome.
Desert and weeds do not form any structural part of the cactus thus they cannot be compared with gene lying of chromosome