What Is the Main Reason for Combining Many Radio Telescopes

What is the main reason for combining many radio telescopes together into an interferometer with large distances between telescopes?

A) to obtain much sharper images of sources
B) to ensure that at least one of the telescopes is in a radio interference-free zone
C) to ensure that observations are uninterrupted by the failure of one or two telescopes
D) to collect more radiation from very faint sources