A "one time pad" can be thought of a Vigenere cipher with A "One Time Pad" can be thought of a Vigenere cipher with... 


An infinitely long key 
A secure symmetric key 
Multiple ciphertext alphabets 
A columnar transposition 


I had this question come up today in one of my mid-terms and to be honest it caught me off guard a little, I chose (2) but I'm having doubts and now thinking its (3). I'm pretty sure i'll get a quick response to this because its quite a basic question, this is from an initial test on intro to cryptography and I felt I did pretty well on the rest of the test but this is bugging me. 

I know one time pad can have infinite period and can be truly unbreakable but that doesn't mean it has an infinitely long key! (does it). (4) is surely a null consideration which leads me to think its (2) or (3)!
(1) is the correct answer.  The Vengiere cipher phrase is a distractor.  Basically all alphabets are in the cipher.

Note that the key does not need to be infinite, merely the same length as the plaintext and random.  So in that regard, all of the answers are incorrect... But (1) is the "best" answer as it is the answer with the most entropy or randomness, which is the point of a one-time pad. You cannot draw any conclusions about entropy from the other answers.