IMO -- D

1) Since the Sum of all the jerseys is (1+2+3+4+5+6+7+8) = 36
For 5 teams it will be 36 * 5 = 180

Since the sum id now 173 for 39 members -- > the jersey number 7 has left the team

2) Since the units digit of the sum of 39 players is 3 we can conclude the numbr 7 has left
Assuming that if number 1 leaves -- sum would be 179
if num 2 leaves -- sum would be 178 and so on..

The units digit of 3 would only come for 173 ,,, hence 7 jersey has left.

thanks