Sickle-cell trait, an allele common in areas where malaria is widespread, Select one: a. if present on only one allele, makes a person resistant to malaria, but if present on both alleles, causes sickle cell anemia. b. can increase the chance that a person will get malaria. c. if present on only one allele, will cause sickle cell anemia, but if on both alleles, makes a person resistant to malaria. d. is not a trait that can be inherited.