__________ our earth, or else it will be no longer fit for us to live on.
| A．Protecting |
| B．To protect |
| C．Protect |
| D．Protected |
A study shows that walking fast in your old age is a ______ that you will live a long life.
| A．sign | B．mark | C．symbol | D．signal |
— Where _______ you put my dictionary?
— I left it on your desk when you _______ to Tom.
| A．did; spoke | B．have; were speaking |
| C．had; were speaking | D．had; spoke |
Raising children is said to be a job _______ parents receive the least formal training.
| A．in which | B．for which | C．where | D．to what |
_______ blood if you can and many lives will be saved.
| A．Giving | B．Give | C．Given | D．To give |
— I saw Dave in the lift this morning.
— Really? He _______ around here for a long time.
| A．won’t be seen | B．wasn’t seen |
| C．hadn’t been seen | D．hasn’t been seen |