Meaning of 'apple of your eye'

[Saneta]

English Language Tests, Intermediate level

ESL/EFL Test #279 "English Slang Idioms (1)", question 3

I spoil my grandson because he's the apple of my ..........

(a) orchard
(b) heart
(c) yard
(d) eye

English Language Tests, Intermediate level

ESL/EFL Test #279 "English Slang Idioms (1)", answer 3

I spoil my grandson because he's the apple of my eye.

Correct answer: (d) eye

Your answer was: incorrect
I spoil my grandson because he's the apple of my heart.
_________________________

what does the expression:,, he's the apple of my eye''mean?
thanks:)

[Skrej]

If someone is the 'apple of your eye', they are appreciated, loved, or cherished above others.
_________________
Plan to be spontaneous tomorrow.
***
Did you hear they arrested the Energizer Bunny on battery charges?
***