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| A．He has just been back from South America. |
| B．He has been burnt for a few hours. |
| C．He has been doing school work all night. |
| D．He has been surfing the Internet for long. |
| A．To look for information for his project. |
| B．To meet new friends in the net chatroom. |
| C．To release pressure from heavy work. |
| D．To look for something interesting for pleasure. |
| A．Quite a few sites are just old event calendars. |
| B．It’s a waste of time to surf the Internet. |
| C．A lot of information can be found. |
| D．A lot of friends can be made on the Internet. |
| A．It takes long to find things because of many useless sites. |
| B．It’s hardly the best source of information available. |
| C．It is hard to start chatting with others in the chatroom. |
| D．People spend much time talking about other interests. |
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
