apple of my eye:

Question

One's favorite person; the one you love most.

In Old English, the pupil of the eye (the round, dark center) was called the 'apple'. It was thought that the pupil was a round object much like an apple. When you look at someone, their reflection appears in your pupil. So if someone is the 'apple of your eye', he or she is someone that you look at a lot and enjoy seeing.
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1. the one you love most.
(What does 'one' refer to? A thing or a person?)

2. the pupil was a round object much like an apple.
(What is the meaning of 'much'? What other expressions can we use instead of 'much'?)

3. When you look at someone, their reflection appears in your pupil.
(Why is' their' used here? Don't we have to use his or her?)

Answer 1

1: A person
2: Similar in appearance to, similar to an apple
3: Their means an object belonging to a person. You could use his or her but their is more appropriate because it can be used for any gender

Answer 2

On question 3, his or her would be better grammar, but we probably would say their instead, as a catch-all or whomever's image is reflected.

KentG is correct on questions 1 and 2 (and mostly correct on 3).

:)