The correct option is D Tightly linked genes on the same chromosome show very few recombination
Recombination is the process of recombining genes on a chromosome to produce organisms with new gene combinations.
Morgan and his group found that when genes were grouped on the same chromosome, some genes were very tightly linked, while others were loosely linked.
The genes which were very tightly linked showed very low recombination whereas those genes that were loosely linked showed higher recombination frequencies.
Hence, in this question, the correct option is "Tightly linked genes on the same chromosome show very few recombination".