The correct option is C Assertion is true but the reason is false
The assertion is true; in a multiple allele system, many alleles are present in a population for a character but the reason is false because an individual contains only two alleles. The best example of multiple alleles is the ABO blood grouping system.
Within the population, possible combinations are IAIA/IAIO,IBIO/IBIB,IAIB,IOIO, but in an individual only one condition of the above combinations is possible.