__ carefully if any change occurs when doing experiments in the lab..
| A．Observe | B．To observe |
| C．Observed | D．Observing |
Your new clothes fit you, but mine me.
| A．doesn't fit | B．don't fit | C．doesn't fit for | D．don't fit for |
Tom's teacher and friend Mr. Smith.
| A．are | B．is | C．are being | D．has |
All that can be eaten eaten up.
| A．are being | B．has been | C．had been | D．have been |
Some person calling for you at the gate.
| A．are | B．is | C．is being | D．will be |
On each side of the street a lot of trees.
| A．stands | B．grow | C．is standing | D．are grown |