Ernie has nailed it, of course. i did think the last clue might have been too revealing, but there weren't a lot of other possibilities left. I can vaguely remember being encouraged to eat carrots to assure good eyesight as a kid in the 1940s. Maybe it even worked: I am still legal to drive without glasses. As I understand it, though, carrots contain things that are good for vision, but so do lots of other things, so most people eating adequate diets don't need large doses of carrots. Whether the carrots-help-eyesight tale was a pre-war story that the Brits used or something they made up for the occasion seems unclear.