Choose the odd one out.

AE
AI
IO
EI E. OU

The odd one out is C, IO. The other options, AE, AI, EI, and OU, are all digraphs, which are two letters that represent a single sound. The letter combination IO does not represent a single sound in English. It can be used to represent two different sounds: the long “i” sound as in “ice” or the long “o” sound as in “go.”

A digraph is a pair of letters that represent a single sound. Some common digraphs in English include:

  • ch: as in “chip”
  • sh: as in “ship”
  • th: as in “thin”
  • wh: as in “white”
  • ea: as in “eat”
  • ai: as in “rain”
  • ei: as in “eight”
  • oi: as in “oil”
  • ou: as in “out”

Digraphs are important because they allow us to represent a wider range of sounds than we could with just the 26 letters of the alphabet.