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This morning I went to the classroom at seven o’clock because I was on duty today. Of course I was the first one. I was cleaning the blackboard when Li Ming came into the classroom. I asked her, “Why do you come here so early?” She answered with a smile, “I know you are on duty today. Let me help you.” I was very happy and said, “Oh, thank you.” We began to work together. When the teacher arrived, we had already done a good job, and the classroom was clean and tidy. The teacher praised me.
1．Li Ming is the first one today. （_____）2．When the teacher arrived, the classroom was clean and tidy. （_____）
3．I was on duty. Li Ming helped me with my work. （_____）
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
