Suppose we encode a text with a Vigenere Cipher using only a single letter as a keyword. Which of the following is true?

Group of answer choices

The result is insecure, since the encryption is equivalent to that of a Caesar Shift Cipher.

The result is fairly secure$,$ since looking for repetitions of three$-$or$-$more characters to determine keyword length will no longer work.

The result is only as secure as an arbitrary monoalphabetic substitution cipher, since it amounts to a single randomly$-$ordered substitution.

The result is as secure as a monoalphabetic substitution cipher with homophones, since multiple ciphertext characters will be used to represent a single plaintext character, but not vice versa.

None of the above are true.