①若{a_n}是“等方差数列”，则数列{a_n²}是等差数列；

②{（﹣1）ⁿ}是“等方差数列”；

③若{a_n}是“等方差数列”，则数列{a_kn}（k∈N^*，k为常数）不可能还是“等方差数列”；

④若{a_n}既是“等方差数列”，又是等差数列，则该数列是常数列．

其中正确的结论是____．（写出所有正确结论的编号）

从所给出的单词中选出合适的完成对话。

supermarket     meat     shopping    rainy    tomatoes

 Tom: Mum, there's no food at home. Let's go ____today.

Mum: But how's the weather?

 Tom: It's a sunny day. It's not____

Mum: OK. Is there any____in the kitchen?

 Tom: No, there isn't.

Mum: Are there any ____or potatoes?

 Tom: There aren't any potatoes but there is only one tomato.

Mum: All right. Let's go to the ____now.