Determine the topic of the question. Question: "who was bush's national security advisor?" Topic:
Ans: Stephen Hadley

Determine the topic of the question. Question: "how old were the twin towers when destroyed?" Topic:
Ans: World Trade Center

Determine the topic of the question. Question: "how many bones are in the skeletal system is composed of 306 bones?" Topic:
Ans: Human skeleton

Determine the topic of the question. Question: "what is metformin used for?" Topic:
Ans: Metformin