General Knowledge · Logical Reading Comprehension

Which choice most logically completes the text? In the South Pacific, New Caledonian crows use two different kinds of stick tools. One tool is complex. The crows shape a stick from a rare plant into a hook. The other tool is basic. The crows find a stick without a hook on the ground. The hooked tool is harder to get but is much better than the basic t ool at removing prey from holes. When studying New Caledonian crows, ecologist Barbara Klump found that they hold the hoo ked tools in their claws when not using them, or they carefully put them in a safe place. The crows don’t do the same with the basic tools. This suggests to Klump that the _________.