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Many people like keeping a dog.Dogs are friendly to people.We call them pet dogs.Dogs are very useful and helpful.A guide dog(导盲犬) is very popular to the blind people.They help people cross the road.The police dogs are used by the police.They help the policemen find the clues(线索) and criminals.
( )1.Dogs are not very helpful.
( )2.Dogs are very useful.
( )3.A guide dog is helpful.
( )4.The police dogs can't help the policemen.
( )5.A guide dog couldn't help the blind people.
同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
