Option D :
is the area of the kite.
Explanation:
The formula to find the area of the kite is given by

where
and
are the diagonals of the kite.
From the figure, we can determine the lengths of the diagonals
and 
The length of the diagonal
is

The length of the diagonal
is

Thus, the lengths of the diagonals
and
are
and
respectively.
Substituting these values in the formula
, we get,



Thus, the area of the kite is 
Hence, Option D is the correct answer.