Complete the concluding sentence of the following paragraph with one of the options given below:
In the 1960s, Jane Goodhall observed chimpanzees removing termites from hides with strapped twigs. Initially, researchers were unable to determine whether the animals viewed a group of tasks as a single problem requiring a general tool set or used individual tools to solve specific tasks. The question was finally resolved when chimps were observed selecting tools to carry with them in anticipation of particular difficulties. Research , therefore, concluded that not only are chimpanzees capable of using tools in a sophisticated way, but they ________