Identify the base present only in RNA

The nitrogen base present only in RNA is uracil.

Form the nucleotide

A nucleotide consists of:

• one nitrogenous base
• one pentose sugar
• one phosphate group

Since it is RNA, the sugar is ribose.

So the nucleotide is uridine monophosphate (UMP).

Count oxygen atoms in each part

(a) Uracil

Uracil has molecular formula: $C_4H_4N_2O_2$ So, oxygen atoms from uracil $=2$.

(b) Ribose

Ribose has molecular formula: $C_5H_{10}O_5$ So, oxygen atoms from ribose $=5$.

(c) Phosphate group

A phosphate group contributes: $PO_4$ So, oxygen atoms from phosphate $=4$.

Total oxygen atoms

Adding all oxygen atoms: $2+5+4=11$

Adjust for condensation during nucleotide formation

While forming the nucleotide:

• base + sugar form a nucleoside, eliminating one $H_2O$
• nucleoside + phosphoric acid form a nucleotide, eliminating one more $H_2O$

Each water molecule removes one oxygen atom from the total count.

Therefore, total oxygens in the final nucleotide: $11-2=9$

Final answer

The number of oxygen atoms present is: $\boxed{9}$