user
Some were big and some were small but they are gone and we don't have to worry at all  What am I?
A: dinosaur
B: big science
C: grain
D: big stick
E: rotunda
assistant
<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

<|end_of_thought|>

<|begin_of_solution|>

A

<|end_of_solution|>