Final answer:
The original sentence without any additional commas is correct: 'Prospective candidates should submit their applications to the human resources department only after the position officially becomes available.'
Step-by-step explanation:
Among the given options, the correct use of commas in the sentence is already present in the original version. Commas should be used before a coordinating conjunction joining main clauses or after an introductory element at the start of a sentence. However, the sentence in question does not have such structures that require a comma. Additionally, commas should not be placed around essential information or after a subject or a verb unless certain conditions apply, none of which are present in this sentence. Therefore, the correct version is the one without any additional commas:
Prospective candidates should submit their applications to the human resources department only after the position officially becomes available.
It's worth noting the verb in the original sentence should be 'becomes' since 'the position' is singular, ensuring subject-verb agreement.