mental ability

In the following series of number’s find out how many times, 1,3 and 7 have appeared together, 7 being in
the middle and 1 and 3 on either side of 7 ?
2 9 7 3 1 7 3 7 7 1 3 3 1 7 3 8 5 7 1 3 7 7 1 7 3 9 0 6
(A) One (B) Two (C) Three (D) Four