In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

Ex Input:
Fact: microbial fuel cells convert chemical energy into electrical energy.

Ex Output:
electrical energy electrons.


Ex Input:
Fact: Placental mammals are therian mammals in which a placenta develops during pregnancy.

Ex Output:
human placental.


Ex Input:
Fact: Chordates have a complete digestive system and a closed circulatory system.

Ex Output:

Chordates are.