.About 71% of the earth’s surface ______ covered with water, but 20% of the world population ______ have access to safe drinking water.
Many soldiers are reported _______ to the drought area to help the local people carry water in the past few weeks.
Three free tickets for the Expo will be given to ________ comes first in the competition.
With the land prices ________, I can’t afford a piece of land big enough to park my car on.
________ is stronger than steel and lighter than a feather is the silk ________ spiders make their webs.
________ you to be the first to solve the structure of DNA?