Answer: C
It is C because when there is a line at the top of the number, it is infinite and repeats many times. That number in a shorter was can be written as a fraction over 990. Two of the answer choices has 990 in it which is letters B and C. This eliminates answer choices A and D. The number that is within the dot is your numerator (645) and 990 is your denominator. Overall the answer is 645/990