Which statement about chimpanzee vocalizations is true?

The statement about chimpanzee vocalizations that is true is that they can vary sounds based on food preferences. This reflects the complexity of chimpanzee communication, which is influenced by their environment and social context. For instance, chimpanzees can produce different vocalizations when they encounter various types of food, signaling to others in their group about the availability or type of food. This variation not only serves to inform others but also highlights their ability to make distinctions based on context and situational needs.

In contrast, while chimpanzees have been observed using forms of gestural communication, including some elements that resemble sign language, this does not encompass all forms of communication they possess. The other options inaccurately represent their vocal capabilities; chimpanzees do not restrict themselves to a single type of sound but utilize a range of calls, and they certainly do understand acoustic differences, which plays a crucial role in their social interactions and environmental awareness.