加热下列物质的稀溶液，可能使离子总数减小的是（不考虑溶液的挥发）（   ）

Dear Daming，

    Thanks for your letter and the wonderful photos. I like them very much.

Here are some of my photos. I'm sending them to you . In the first photo，it is snowing. I'm making a snowman with my friends. In the second one，the sun is shining and the wind is blowing. I'm flying a kite in the park. In the third one，I'm swimming in the sea. In the last one，I am with my sister Lucy. We're playing chess.

Best wishes to you and your family.

Love，

Jack

根据书信内容选择正确答案。

今大道既隐，天下为家，各亲其亲，各子其子，货力为己，大人世及以为礼。

──《礼记·礼运篇》

请回答：

温室效应是由于进入大气中的（ ）为主的气体增加产生的．