In the drop down box, "el aguja", "la torre" and "el campanario" are given for the "the steeple". We should get credit if we give one of those as an answer.
Strictly architecturally speaking, "una aguja" would be a steeple. "Aguja" also means needle. A steeple is a type of tower ("torre"), so although it would not be incorrect to say that a steeple is "una torre", the correct word would be "aguja".