Answer: Any pencil label from 4B to 8B
Explanation:
Your H labels on pencils tend to show that the pencil has a softer lead. Therefore the B lables on pencil have harder leads.
See attached image for an image of my explanation.
That is "Fountain" by Marcel Duchamp
The aspect of of instruments that improved during the Romantic period was the valves. The correct answer is D, valves.