一篇英语阅读理解(只有一道题）

一篇英语阅读理解(只有一道题）
Let’s look at some old inventions we use every day.
Bubble gum
Bubble gum was invented by accident.In 1928,American gum company worker Walter E.Diemer played around with new chewing gum recipes.Chewing gum had already been invented more than half a century before then.But Diemer found that the gum he made was less sticky (粘的) and easier to stretch (伸展).He blew a bubble and then saw the possibilities.He took some of his new gum to a shop and it sold out in a single afternoon.Since then,Dubble Bubble－the first name for bubble gum－has made kids happy all around the world.
1 Bubble gum was invented around____years after chewing gum was invented
A30 B50 C80 D100