That is accepted, except when it's a listening exercise due to the difference in pronunciation.
Normally it's "je bent een jongen" but when verb and "je" are inversed, it's "ben je een jongen?"
Dropping the -t for "je"
When a sentence is inverted, that is, the verb comes before the subject, an odd thing can happen: if the subject is je (or the stressed form "jij"), then the verb loses the -t at the end.
- Je spreekt Nederlands. - You speak Dutch.
- Spreek je Nederlands? - Do you speak Dutch?
This does not happen for any other subject, like hij or ze! So keep a close eye out for the combination of inversion + je.