Before answering the question, you should know that exons/intron systemin the gene exists only in eukaryotes. A gene can have many exons with introns between them, but in RNA maturation, these exons will be joined together to form one RNA to code for one protein (There's no relation between exons number and how many proteins are formed).
In prokaryotes it is different there's no exons/introns, but their gene can be transcripted to a polycistronic RNA which can give after translation more than one proteins.
Answer: Possibly increase the production of socks
Explanation: As it implies, the mosquitoes that have sickness land on socks more often. Based on this information, since we know that malaria comes from mosquitoes, we can increase the production of socks, as that will separate most of the infected mosquitoes with the other mosquitoes, as most of the infected ones will fly over to the sock. With this scenario, we can bait the mosquitoes and know which ones are infected
The answer is A- mesophyll