Task: Question Answering
Input (English): Passage: In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry. Question: Air-dried wood keeps up to what percentage of the water in its cell walls?
Output (English): 16