the addition of which of the following sentences would create an effective paragraph? dogs and cats are both fantastic pets. dogs are loving and playful. cats are clean and self-sufficient. dogs are sometimes hyper. (select a, b, c, or d and place here.) both are effective communicators in their own right. either one would make any lucky owner happy. 

C. Cats are normally calm and resigned.

In this excerpt, the author is comparing the qualities of dogs and cats. He argues that they are both fantastic pets. He compares them side by side, and sentence by sentence. The next logical sentence, due to this structure, is one about cats. Specifically, the author should discuss whether cats are hyper like dogs, or whether their energy levels are different.