Question

if density D , acceleration a , and force F are taken as basic quantities then time period has dimensions?

Answer 1

the density has dimension $ML^{-3}$
so take that as D 
the acceleration has dimension $LT^{-2}$
take it as A
the force has dimension $MLT^{-2}$
Take it as F
so time period has dimension as $D^{ -\frac{1}{6} }A^{ -\frac{2}{3} }F^{ \frac{1}{6} }$
actual dimension is T for time