Question

review the details below.
dr. carl sagan wrote a highly popular companion book for the series cosmos, as well as the follow - up book pale blue dot: a vision of the human future in space.
dr. carl sagan was the co - host and co - writer of cosmos: a personal voyage, a thirteen - part pbs series watched by 750 million people.
as an astronomy and space sciences professor at cornell university, dr. carl sagan edited a scientific journal, published books, and appeared frequently as a guest on late - night talk shows.
choose the best topic sentence to introduce a paragraph containing these details.
dr. carl sagan used his credibility as an academic to co - host and co - write cosmos: a personal voyage.
dr. carl sagan was a gifted communicator who used his vast knowledge to share scientific topics with millions of people.
tv series and books designed for the average person are the best ways to get the public interested in scientific topics.

Explanation:

The details mention Dr. Carl Sagan's academic role (professor), his work in writing books (companion book for Cosmos and Pale Blue Dot), co - hosting and co - writing a popular TV series (Cosmos: A Personal Voyage watched by 750 million people), and his appearances on talk shows. The first option only focuses on one aspect (co - hosting and co - writing Cosmos). The third option is about TV series and books in general, not specifically about Dr. Carl Sagan. The second option encompasses his role as a communicator (through books, TV series, talk shows) using his knowledge (as a professor) to share scientific topics with a large number of people (750 million for the TV series).

Answer:

Dr. Carl Sagan was a gifted communicator who used his vast knowledge to share scientific topics with millions of people.