Final answer:
Fluorine has the smallest atomic radius among the given options.
Step-by-step explanation:
The element with the smallest atomic radius among the given options is fluorine (option d). Atomic radius refers to the size of an atom, and it is determined by the number of electron shells and the effective nuclear charge. Fluorine has the highest effective nuclear charge among the elements listed, which pulls the electrons closer to the nucleus, resulting in a smaller atomic radius.