我国四大工业区中，以重工业为主的是（　　）

C

    There is a big demand (需求) for English teachers in China. The country develops at a high speed, so it needs lots of volunteers who can teach primary school students conversational (对话的) English skills in China. Global Crossroad is mainly connected with several Chinese public schools. And most of them are in the countryside. Non-native English speakers are also invited to join this project.

    With the growth of the country's economy, the demand for English education in China is growing. As China continues to be a global business country, the importance of English education is increasing as well. Many public schools in China have an "English Comer", which is a place of the classroom designed (设计) and set aside for teaching and learning English. These schools are in need of international teachers to teach English.

    Most schools in the countryside in China are searching for good English teachers. Your time and efforts are so important in improving these students' English skills and helping them get more equal (平等的) chances to work in the future.

经测定Na₂SO₄ 在不同温度时的溶解度数据如下表：

下图是表示随温度变化饱和溶液溶质质量分数的变化曲线，其中能表示随温度变化饱和溶液中溶质质量分数变化曲线的是（   ）