Since each group depends upon the other groups. a. fragment b. run-on c. correct

The answer is:  [A]: fragment .

The phrase:  "Since each group depends upon the other groups."

is NOT correct as it is — thus eliminating "Answer choice: [C]: correct" ; 

and is NOT a  'run-on sentence' — thus eliminating
                                                  "Answer choice: [B]: run-on" .

Rather, the phrase:

 "Since each group depends upon the other groups."  ;

  is a sentence FRAGMENT; which is the remaining answer choice given—  
"Answer choice:  [A]:  fragment" .

Is there a dictionary to use?