Question: There are two types of modern whales: toothed whales and baleen whales. Baleen whales filter plankton from the water using baleen, plates made of fibrous proteins that grow from the roof of their mouths. The embryos of baleen whales have teeth in their upper jaws. As the embryos develop, the teeth are replaced with baleen. Which of the following conclusions is best supported by this information?

  Options: 
 A. Primitive whales had teeth as adults.
 B. Toothed whales descended from baleen whales.
 C. Baleen whales are evolving into toothed whales.
 D. Descendants of modern baleen whales will have both teeth and baleen as adults. 
Answer: A