The shift operator E is defined as
$$ E [f(X_i)] = f (X_i + h) $$ and $$ E^{-1} [f(X_i)] = f (X_i - h) $$
Then $$ \triangle $$ (forward difference) in terms of E is

A

$$ E - 1 $$

B

$$ E $$

C

$$ 1 - E^{-1} $$

D

$$ 1 - E $$