Choose the correct option A, B or C to complete the text.

I'd like to tell you about a product which makes a huge difference to my life - contact lenses. They're just thin circles of plastic, but if they 1, it would have been much harder for me to play sports. Contact lenses 2 available to the public in the early 1970s. However, the science that makes them work 3 almost 500 years earlier by Leonardo Da Vinci. He 4 a link between looking through water and seeing more clearly. Over the next three hundred years, various different experiments 5 with glass tubes, water and glue. A big breakthrough came late in the 19th century, when the first eye-shaped glass lens 6 However, it was heavy and impractical. Advances in technology 7 in the 20th century led to the use of plastic for the first time, and eventually to the production of softer, lighter, more comfortable lenses which could 8 for longer. I don't know what I'd do without them!

1 A hadn't been invented B hadn't invented C didn't be invented
2 A were become B became C were became
3 A discovered B had discovered C had been discovered
4 A had been found B had found C was found 
5 A did B have been done C were done
6 A was created B is created C created
7 A making B being made C are making
8 A wear B were worn C be worn