Marked me wrong for putting "police" without the addition of "force" too. It is acceptable English to just use the word "police" and seems like a reasonable translation of the Greek text.
The goal of this course is to help people learn a new language. The fact that one can infer that a police officer has probably something to do with a police station doesn't mean that we should use "police station (=αστυνομικό τμήμα)" as a translation for "αστυνομία".