—I hear you have an experience in the Royal Air Force. Is that ture?—Yes. I ______ in the Royal Air Force for six years. A. served B had served C joined D have joined
They were so far away that I couldn't _____ their faces clearly.
If the boy had _____ the dog alone it wouldn't have bitten him.
The generation _____ makes it difficult for parents to understand their children's opinions.
With sufficient scientific information a manned trip to Mars should be _____.
_____ inviting guests and not treating them properly!