You HAVE to type your occupation. What options are you talking about?
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
It seems you are trying to apply for the N-400 electronically, online. Always a bad idea! As you can see you are having difficulties, that could get your case denied, or at least unnecessarily considerably delay you. File the N-400 the old fashioned way, by mailing it. You'll be much better off for that. Then you can type in the "occupation" that you feel best describes what you do, and you won't have to struggle with an incomplete "drop down" menu.
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Don't let some pdf form-filling program limit you. Leave it blank, print the form, hand write the truth.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.