Question

Read the title and subtitle from "Majority of Americans Believe It Is Essential That the U.S. Remain a Global Leader in Space.”

Majority of Americans Believe It Is Essential That the U.S. Remain a Global Leader in Space: Despite the Increasing Role of Private Companies in Space Exploration, Most Believe NASA’s Role Is Still Vital for Future

What is the purpose of the subtitle?

to signal order of importance
to provide more extensive information about ideas in the text
to signal important details
to provide additional information about the topic of the text

Answer 1

to provide additional information about the topic of the text

The subtitle expands on the title by adding a key detail (private companies' growing role vs. NASA’s continued importance).