Information and Ideas practice question

The naturalist spent every dawn for a year at the same bend of the river and wrote down only what she saw, never what she expected. Her notebook is full of absences: the kingfisher that did not come, the fog that hid the far bank, the hour in which nothing happened. It is those absences that later readers have found most useful, because they say when and how often the river was empty, which no one else had thought to record.