Correct Option: C

Let us assume that two consecutive even numbers are P and P + 2.
According to given question,
(P + 2)² – P² = 84
⇒  P² + 4P + 4 – P² = 84
⇒  4P = 84 – 4 = 80

⇒  P =	80	= 20
	4

⇒  P + 2 = 20 + 2 = 22
∴  The required sum = 20 + 22 = 42
2nd method
Let us assume that two consecutive even numbers are P and P + 2.
According to given question,
(P + 2)² – P² = 84
Use the formula a² – b² = ( a + b )( a - b)
⇒ ( P + 2 + P )( P + 2 - P ) = 84
⇒ ( P + 2 + P )( 2 ) = 84
⇒ ( P + 2 + P ) = 84/2
⇒ ( P + 2 + P ) = 42