The word "account" has multiple meanings depending on context:
As a noun, it can mean a banking record or a description/record of events.
As a verb, it means to explain, justify, or consider, but it is usually used with a preposition (e.g., account for something), not as a standalone verb.
Sentence I: Correct - "savings account" is an appropriate noun usage, meaning a financial record at a bank.
Sentence II: Correct - "a detailed account of the events" is also correct, where "account" means a description or narrative.
Sentence III: Incorrect - The word "account" doesn't make the sentence meaningful, and thus the phrasing "will account the employees" is wrong. The appropriate word would be "credit", and thus the correct form would be "will credit the employees."
Hence, the correct answer is option (c): Both I and II.