Use 'A' in a Sentence

At Domu's school, they are now teaching spelling. Each pupil is given their own set of words. They seem to be easing Domu slowly, since his assignment is to learn how to spell the following words: a, is,in, and, be, I. Those were very easy for him, since in Hong Kong he was already at the stage where he'd been reading and writing two-character Chinese phrases.

To make the spelling practice a little tougher at home, we made him both spell the word and use it in a sentence.

Me: Spell 'A'
Domu: 'A'
Me: Use 'a' in a sentence
Domu: We went to Australia.
Me: Huh? Where's the a?
Domu: Australia begins with 'A'.