They always lay a large supply of tinned food in winter in case they are snowed up.
| A．out | B．off | C．in | D．with |
I have told you the truth. ______ I keep repeating it?
| A．Must | B．Can | C．May | D．Will |
Their relationship_______ ups and downs over the past century.
| A．will see | B．sees |
| C．has seen | D．had seen |
________carefully if any change occurs when doing experiments in the lab.
| A．Observe | B．To observe |
| C．Observed | D．Observing |
______ before bed, cellphones can result in a restless night.
| A．To use | B．Using | C．Used | D．Having used |
Love is_____ makes you smile when you are tired.
| A．that | B．what | C．it | D．which |