A population contains equal number of individual with the genotypes AA and Aa proportion of alleles A and a in the gametes will be1)3:12)1:13)1:24) can`t be determined

AA can produce gametes with allele A while Aa can produce gametes with allele A and a as well. AA cannot produce gametes with allele a so probably only Aa has to be taken into superficial consideration which sows A:a = 1:1.