The discovery of planets outside our solar system is of great importance, ----.
A) as individual dust particles are so small
B) because the triangle of light stretches along the Sun’s path in the sky
C) since it is the first tangible clue that we may not be alone in the universe
D) if one can communicate with extraterrestrial beings
E) whether similar collections of worlds surround other stars in the galaxy
The suggested answer is "C". Could anyone explain the differences between A, B, C in terms of their using following a comma?
Thanks in advance![Smile [:)]](/emoticons/emotion-1.gif)