Plants are an important food for many living things, including humans. Plant eaters are animals that eat plants. They can be large, like cows, sheep, or horses, but most of them are actually much tinier, such as caterpillars (毛虫).
With so many creatures trying to attack (攻击) plants, you can imagine that they have a hard time living. Since plants cannot run away from their attackers, they have to develop different ways of protecting themselves.
Plants have developed several defenses (防御物) against animals that eat plants. Roses look pretty and small good. They aren't very strong, but they have thorns to frighten away animals. So the animals can't eat their beautiful flowers. Cacti (仙人掌) live in the hot, dry desert. Animals would like to drink the water and juice in these plants. so cacti cover their bodies with many thorns. These thorns can hurt animals. Some trees have sharp leaves. These leaves can also keep animals away.
Other defenses, such as chemical defenses, can be seen less. Each plant produces thousands of different chemicals. Some chemicals, like sugars, give energy to the plant. Other groups of chemicals help to defend plants against attackers. These chemical defenses can make the plant taste bad, which prevents animals from eating the plant. Tomatoes make their leaves taste very bad so that animals don't like to eat them. There are many plants that will make you feel sick if you eat them, such as the fruit of the black nightshade (茄属拉物). Some plants, like poison ivy or hog. weed (毒常青藤或猪草), can even cause burns when you touch them. Most chemical defenses aren't that bad, though.
Plants use these defenses to stay alive. They keep plants safe from hungry animals.
B . 
C . 
D . 
