题目内容：
根据下列短文，回答题。Climate．more than any other single factor，determines the distribution of life on earth．Cli-matic boundaries establish the limits which organisms can survive．Plants，even more than ani-mals．must be well adapted to climate in order to survive．They cannot move about or take shel-ter but must be equipped to endure whatever weather conditions are likely to Occur．In the harsh conditions of the tundra，for example，low growing mosses，lichens，and a few flowering plants allhug the ground for shelter from icy winds．
Animals，despite their ability to move about and find shelter，are just as much influenced by climate as plants are．Creatures such as the camel and the penguin are so highly specializedthat they have an extremely limited distribution。Others，such as bears are flexible"enough to a．dapt to a broad range of climates．Oceandwelling organisms are just as sensitive to climaticchanges--in this case temperature and salinity--as land animals．Reef corals can survive onlyin clear warm seawater．Certain foraminifers are so sensitive to changes in their environmentthat their presence can be taken as an index of sea temperature．Human beings are among theleast specialized of all animals and can live almost anywhere．Their clothes and their homes actas a sort of“miniature climate”that Can be taken with them everywhere．
According to the passage，plants on the tundra grow in the ground_________． A．to avoid being eaten by arctic animals
B．because fertilizer is not readily available
C．to minimize exposure to the cold
D．because unfrozen water supplies are very scarce
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