The radiation intensity of a given anteena is $$U = 2 (\sin \theta \sin \phi)$$ in the range $$0 \leq \theta \leq \pi$$ and $$0 \leq \phi \leq \pi$$ and 0 else where .The directivity is

A

3 dB

B

6 dB

C

8 dB

D

9 db