If your mother wants to tell you something, she uses words. Birds cannot talk as we do. But some birds can make sounds to warn their young of danger.
The jackdaw is a kind of blackbirds that lives in Europe. Jackdaws live together. Young jackdaws do not know their enemies. When an older jackdaw sees a dog, it makes a loud rattling sound. The younger birds know this sound means danger is nearby. The sound warns them to know their enemies.
If a young jackdaw is in a dangerous place, a jackdaw parent flies over him from behind. The parent bird flies low over the young bird’s back. The parent’s tail feathers move quickly from side to side, trying to express, “Follow me.” At the same time, the parent calls out, “Key-aw, key-aw. ”The parent mean, “Fly home with me.” The young bird then follows the older one home. Young jackdaws do not have to learn what certain sounds mean. They know the meaning of these sounds from the time they hatch（孵出）.
小题1:The jackdaw lives in .
A．Europe
B．Australia
C．America
D．Africa小题2:Which of the following does this story lead you to believe?
A．All animal parents can talk to their young.
B．Dogs are the most dangerous enemies for jackdaws.
C．Young jackdaws know the meaning of their parents’ sound when they grow older.
D．Some birds can give information to one another.小题3:Parent jackdaw can use their tail feathers to .
A．ask their young to follow them
B．play a game with the young
C．tell the meal time
D．give a warning of a fire
，从某一高处水平抛出，到A点时速度方向恰好沿AB方向，并沿倾斜轨道滑下。已知物块与倾斜轨道的动摩擦因数
（g取10m/s2，
）