Answer : The correct answer for the blank is -
d. dna molecules.
DNA ( deoxyribonucleic acid) is considered as the genetic material of living organisms. It is passed from one generation to the next generation (that is from parents to their offspring).
The genetic information is present in DNA in the form of nucleotide sequences. It carries all the essential information that is required by an organism for the survival, growth and development, as well as reproduction.
Thus, option d) is the right answer.