When to use 'a' or 'an'

Generally speaking we use 'a' if the next word has a beginning consonant sound and 'an' if the next word begins with a vowel sound. However there are exceptions and confusions.
E.g. I will buy a house in an hour. both house and hour begin with the letter 'h' but it is silent in hour so you use 'an'
Now try the test. Click onto 'a' and 'an' test below and click on the one you think belongs.

take the 'a' and 'an' test.