SAT English Practice Question

While some scientists have argued that the ability of giraffes to make low-pitched humming sounds is a sign of intelligence, others have suggested that the humming noises are merely a form of communication between giraffes in a specific situation that doesn’t require complex thought. The researchers claim that giraffes, which have an excellent sense of vision and are able to see in color, only produce the humming sounds when it’s impossible for them to signal to one another visually, such as at night when they can’t see one another. The fact that the giraffes only produced the humming sounds at night when they couldn’t see one another, therefore, ______

1. A.suggests that giraffes are more intelligent than scientists had previously believed.
2. B.is not conclusive evidence that the humming sounds are an indication of intelligence.
3. C.indicates that the humming sounds are a complex form of communication, not a simple signal.
4. D.eliminates the possibility that the humming sounds are used as a simple signal.