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Lingling: Yes. There wasn’t a big lake three years ago. And there weren’t any ducks.
Sam: Look. There are lots of tall trees.
Lingling: There were lots of small trees three years ago.
Sam: Let’s feed the ducks, OK?
Lingling: Oh, no, Sam. Look at the sign: Don’t feed the ducks. Let’s take some photos of ducks, OK?
Sam: That’s OK.
1．There isn’t a big lake in the park.
2．There weren’t any ducks.
3．There are big trees.
4．Sam and Lingling can feed the ducks.
5．They will take some photos of trees.
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
