Which of the following statements is the best choice to validate user input when entering a marital status as a single letter?

Question

BlackTom AI · Accepted Answer

Question restated: Which of the following statements is the best choice to validate user input when entering a marital status as a single letter?

Option 1: if maritalStatus == "S" or maritalStatus == "M" :
This checks for uppercase S or M only. If the user enters lowercase s or m, this will fail. It is incomplete because it ignores valid lowercase inputs.

Option 2: if maritalStatus == "s" or maritalStatus == "m" :
This checks for lowercase s or m only. If the user enters uppercase S or M, this will fail. It is incomplete because it ignores valid uppercase inputs.

Option 3: if (maritalStatus == "s" or maritalStatus == "m" or
    maritalStatus == "S" or maritalStatus == "M") :
This combines both lowercase and uppercase checks in a single expression, covering all four valid single-letter inputs (s, m, S, M). The line break does not affect logic and the condition is explicit about all accepted cases, making it robust for typical input validation.

Option 4: if maritalStatus == "s" or "S" or "m" or "M" :
This is misleading in many languages. The expression will evaluate as (maritalStatus == "s") or ("S") or ("m") or ("M"), and non-empty string literals like "S", "m", or "M" are truthy, causing the condition to almost always be true regardless of the actual input. It does not correctly validate the user input and introduces a logical error.

Summary of reasoning across options: Option 1 and Option 2 each handle only one case style (uppercase or lowercase), leaving out valid inputs. Option 4 presents a common pitfall by mixing a comparison with bare string literals, which leads to an always-true condition in many languages. Option 3 provides a complete and explicit check for all valid single-letter inputs, ensuring that either 's', 'm', 'S', or 'M' will pass the validation while other inputs will fail.

Which of the following statements is the best choice to validate user input when entering a marital status as a single letter?单项选择题

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