Two idential straight wires are stretched so as to produce `6` beats per second when vibrating simultaneously. On changing the tension slightly in one of them, the beat frequency remains unchanged. Denoting by `T_(1)`, `T_(2)` the higher and the lower initial tension in the strings, then it could be said that while making the above changes in tension,
A. `T_(2)` was decreased
B. `T_(2)` was increased
C. `T_(1)` was increased
D. `T_(1)` was kept constant