And it's spelled "civilized".
That's why you only got a 4.
Oxford Advanced Learner's Dictionary of Current English spells it that way.
You might want to read what it says, then. "-ise" is listed as an acceptable spelling. But then, we've already established that you lack in that area.
I believe Fowler was partial to the "-ize" form, arguing from Greek's "izo", regardless of the origin of the word being discussed. However, most credible dictionaries will list both as acceptable; even Merriam-Webster's 3rd edition lists "ise" as the British spelling.