-Our classroom__________ every day.-So it is. It’s our duty to keep it clean and tidy.A. cleans B. is cleaning C. is cleaned
Tom and Jim are talking. We should tell them _______ noise while watching birds.
---_______ do people cut down so many trees here?--- To get enough space for a new road.
--- Red-crowned cranes need more people’s help.---Yes. People working in the reserves are doing everything they can ____these birds.
---I often hear a new-born baby next door __________ a lot at night.---Maybe the baby is hungry then.
About seventy percent of our earth _______ by water.