材料用具：澄清石灰水、试管2支、气球2个、打气泵1个、凡士林、细线若干条。

设计方案：

步骤一：把气球A吹到一定大小，并用细线扎紧气球口，接着用打气泵向气球B打入空气，使其与气球A一样大，也扎紧气球口。

步骤二：向甲、乙两支试管中分别加入3毫升澄清石灰水。

步骤三：在甲、乙试管外壁涂上凡士林，减少实验时气体外泄。

步骤四：把气球A和B分别套在试管甲和乙上(如图所示)，解开气球，将球内气体通入试管，并轻轻振荡。

步骤五：观察甲、乙试管内石灰水的变化。

根据以上实验设计，回答下列问题。

等差数列$\left\{a_n\right\}$及等比数列$\left\{b_n\right\}$中，$a_1=b_1>0,a_2=b_2>0$则当$n\ge 3$时有（    ）

——Why ________  your father like koalas?

——Because they are ________ interesting.

根据短文理解选择答案。

      It is Sunday today. Ann is shopping with her mother. She wants her mother to buy a sweater for her.

      In a clothes shop, she finds an orange one. She tries it on, but it's too small. She wants a bigger one, but the bigger ones are not orange. Ann doesn’t like other colours. Her mother asks, "Shall we go to another shop to have a look?" So they go out of this shop and go into another.

      The second shop is much bigger than the first, and in it there are many kinds of sweaters of different sizes and colours. Ann tries on an orange one. It's too big. She tries a smaller one. It's OK.

   “How much is it?” Ann’s mother asks the woman who sells clothes.

      Then they find it too expensive, and they don't have so much money with them.

    “Would you like a cheaper one?” The woman asks.

    “No, we shall take this one. My daughter likes it. We shall come back to buy tomorrow.” Ann's mother answers.

      After that, they leave the shop to buy some other things.