Answer; 
-Made of nucleotides
Explanation; 
The part B of the Venn diagram shows similarity between the RNA and DNA. -DNA and RNA  are nucleic acids of nitrogen-containing bases joined by sugar-phosphate backbone. They are made up of monomers called nucleotides.  Both have 3 nitrogenous bases: Adenine, Cytosine and Guanine. They also have a phosphate groups in their nucleotides. 
-DNA and RNA also differ in a number of ways which includes;  RNA is a single-stranded where as DNA is double stranded, DNA has Thymine, where as RNA has Uracil, etc.