| 已知数列A：a1，a2，…，an（0≤a1＜a2＜…＜an， n≥3)具有性质P：对任意i，j(1≤i≤j≤n)，aj+ai与aj-ai两数中至少有一个是该数列中的项， 现给出以下四个命题： ①数列0，1，3具有性质P； ②数列0，2，4，6具有性质P； ③若数列A具有性质P，则a1=0； ④若数列a1，a2，a3（0≤a1＜a2＜a3）具有性质P，则a1+a3=2a2； 其中真命题有 |
A.4个 B.3个 C.2个 D.l个 |
答案：B
| 完形填空。 | ||||
| How do you get pocket money (零花钱) from your arents? In the western countries,many__ l _ do housework to get pocket money. They usually start to do this __2_ the age of ten. Jimmy is seven years old. Now he _ 3_ the dishes. He can only do this, so he can't get _4 _ money. But that's all right. He only wants to _5_ candy. Jenny is twelve years old. She is _6_ than Jimmy. She wants to buy many things. They are _ 7_ than candy. So she has to work harder! Now she is washing the car. If she 8 free time , she will cut the grass ,walk the dog or cook dinner. Doing housework can _9_ kids learn new things. For example , you can learn how to cook. Of course , your _10 _ will help you at the beginning.
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