The correct answer is Option B: Adenylic acid. Here's why:

Let's break down the components of a nucleotide:

• Sugar: A five-carbon sugar, either ribose (in RNA) or deoxyribose (in DNA).
• Phosphate Group: A molecule containing phosphorus and oxygen, often attached to the sugar.
• Nitrogenous Base: A molecule with nitrogen-containing rings, such as adenine (A), guanine (G), cytosine (C), thymine (T), or uracil (U).

Now let's analyze the options:

• Option A: Uridine is a nucleoside. It consists of the nitrogenous base uracil and the sugar ribose but lacks the phosphate group.
• Option B: Adenylic acid is a nucleotide. It consists of adenine, ribose, and a phosphate group.
• Option C: Guanine is a nitrogenous base, a component of nucleotides, but not a complete nucleotide itself.
• Option D: Guanosine is a nucleoside. It comprises guanine and ribose but lacks the phosphate group.

Therefore, Adenylic acid is the only option that contains all three components (sugar, phosphate, and nitrogenous base) required to be a complete nucleotide.