Complete the lead scientist's mission log about a strange extraterrestrial discovery.

The alien diet, primarily _____ of glowing blue rocks and cosmic dust, has fascinated our nutritionists for months.

The correct answer is consisting.

The original non-defining relative clause is "which primarily consists of...". Because the verb "consist" is active, we reduce it to the present participle consisting.

This is a common trap! Students often choose "consisted" because it sounds like the passive phrase "composed of." However, the verb "consist" is strictly intransitive and can never be passive. Therefore, it must be reduced using the active "-ing" form.