Correct Answer - A

Given, `g_(m)=1.7 ms^(-2),g_(e)=9.8 ms^(-2)`

`T_(m) = ? and T = 3.5 s`

As `T_(e)=2pi sqrt((l)/(g_(e)))`

and `T_(m)=2pi sqrt((l)/(g_(m)))`

`therefore" "(T_(m))/(T_(e))=sqrt(g_(e)/(g_(m))) or T_(m)=T_(e) sqrt((g_(e))/(g_(m)))`

`rArr" "T_(m) = 3.5 sqrt((9.8)/(1.7))=8.4 s`