Final answer:
To identify an allele that has experienced recent strong positive selection, measuring average heterozygosity, assessing the fraction of loci out of Hardy-Weinberg equilibrium, and determining the fraction of marker-locus pairs in linkage disequilibrium are all effective methods. Therefore, the correct answer is d. All of the above.
Explanation :
Linkage disequilibrium occurs when alleles at different loci are associated with each other more frequently than would be expected by chance. A high level of linkage disequilibrium may indicate that a selective sweep has occurred recently, where a beneficial allele has rapidly increased in frequency, bringing along nearby alleles.
Therefore, the correct answer is d. All of the above. By examining all these parameters, scientists can get a comprehensive view of evolutionary forces affecting allele frequencies, allowing them to infer that certain alleles have been subject to strong positive selection.