The correct statement is:
Mendelian inheritance concerns genetic traits that are controlled by only two alleles, while non-Mendelian inheritance is controlled by multiple alleles.
This accurately reflects the distinction between Mendelian inheritance, which typically involves traits governed by a single pair of alleles (dominant and recessive), and non-Mendelian inheritance, which can involve multiple alleles, polygenic traits, or incomplete dominance, among other complex patterns.