It's ten years since the scientist _______to discover the valuable chemical.

 Recently，these companies have ________ some workers becames of the drop in economy.

 We recently did a simple experiment, which happens to ________ how children's knowledge of what a hero is like determines their behaviour.

To his satisfaction，he got_____people voting for him as he thought.

  ----Why don’t you ______ to a more sensible method? ----Well, I’m thinking about it.