Let x be the marks sunita obtained in the fifth examination.
Total marks obtained in all five examination is
$87 +92+94 +95+x $
To get grade A the average must be greater than or equal 90.
Thus $ \large\frac{87 +92+94 +95+x}{5} $$ \geq 90$
$=> \large\frac{368 +x}{5} $$ \geq 90$
Multiplying both sides by positive number 5.
$=> 368 +x \geq 450$
Subtracting 368 from both sides,
$=> x \leq 450 -368$
$=> x \geq 82$
Step 2:
Sunitha must obtain atleast 82 marks to get grade A.
Hence D is the correct answer.