A) Nitrogen B) Hydrogen C) Carbon dioxide D) Oxygen
A) Fruit B) Leaves C) Roots D) Bark
A) The clearing of trees in an area. B) The planting of trees. C) The conservation of forests. D) The protection of endangered species.
A) Maple B) Willow C) Birch D) Pine
A) About 15% B) About 31% C) About 50% D) About 75%
A) They grow underwater. B) They absorb heat. C) They consume carbon dioxide only. D) They produce oxygen through photosynthesis.
A) Oxygen B) Carbon monoxide C) Nitrogen gas D) Sulfur dioxide
A) They decrease populations. B) They increase pollution. C) They create deserts. D) They provide shelter and food. |