What ________ you ________ at this time yesterday

Wind power is an ancient source of energy wemay return in the near future.

generally believe that women are more emotionalthan men, but in my experience that often is not the______.

_______ will the fog and haze(雾霾) last —I have no idea. There is no sign of an end.

Yesterday, a man said he saw _______ UFO in the park. The police are looking for _______ UFO now.