A pendulum suspended from the roof of an elevator at rest has a time period `T_(1)`, when the elevatore moves up with an acceleration `a` its time period becomes `T_(2)`, when the elevator moves down with an acceleration `a`, its time period becomes `T_(3)`, then
A. `T_(1)=(T_(2)+T_(3))/(2)`
B. `T_(1)=sqrt(T_(2)+T_(3))`
C. `T_(1)=(T_(2)+T_(3))/sqrt(T_(2)^(2)+T_(3)^(2))`
D. `T_(1)=(sqrt(2)T_(2)T_(3))/sqrt(T_(2)^(2)+T_(3)^(2))`