Read this sentence from the passage. He invented a machine called the crescograph, which could detect tiny movements within plant tissue when exposed to things like light or harmful substances. How does this sentence contribute to the overall idea in paragraph 3?

A. It suggests that people are already aware that plants could detect changes.
B. It compares crescographs to other machines by showing the similarities between them.
C. It describes how crescographs work to explain the term "natural sciences."
D. It explains the function of a crescograph to familiarize the readers with the device.