Answer:
A. to shield them from electromagnetic interference
Explanation:
Radio observatories have to be placed away from urban centers to avoid electromagnetic interference from radio, television and other man-made devices. They have to be shielded since they detect the radio waves from astronomical radio sources. This type of observatory observes the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects. In contrast, the optical telescopes observe the light wave portion of the spectrum coming from astronomical objects.
