Communication Satellites which evidence from the passage

This  line from the passage "Signals, which travel in straight lines, could not bend around Earth to reach a destination far away." supports the claim that before communication satellites existed, people could only send signals over short distances

Explanation:

The author  in the passage mentions that before communication satellite people used to send message through signal(like a radio signal,telegram signal etc) but the main constrain of sending the message through a signal was that the signal travel in a straight line and it cannot be bend as per the earths curvature.So,it was not possible to send signals at distance place .

Lets consider a person sitting in Singapore cannot send signal to the person in America the basic reason for this is the earths curvature and the straight line pattern of signal transmission

So by using the signal technology one can send message to people residing in same cities or state.Long Distance communication was not possible through signal transmission.

c is the answer because first she would blush to make the reader wonder why which they find out in the next line.