also, just a note for the course administrators...
i am marked incorrect if i type in 'mum', and told the correct word as 'mom'. it is only one letter different, but here it is treating my answer as incorrect, rather than as just a typo.
'mom' is american english. in australia, new zealand and england it's 'mum'. please, it would be great if you could add 'mum' to your database as well :)