It's terrific fun to read what the original thinkers had to say for themselves. I read parts of Relativity: The Special and General Theory by Albert Einstein, and found the letter about Einstein forgetting to eat lunch in Einstein: His Life and Universe by Walter Isaacson.

—A Black Hole Is NOT a Hole,
Carolyn Cinami DeCristofano

Choose the most likely reason why the author selected Einstein's work as a source for her book.

It was published recently.
It contains Einstein's opinion.
It uses serious language.
It reflects Einstein's expert knowledge.