3 sentences

1. 北方人的主食通常是面食。

   běi​fāng rén de zhǔ​shí tōng​cháng shì miàn​shí.

   The staple food for northerners is usually wheat-based products.

   Source: Dong Chinese Dictionary

2. 南方人习惯以大米为主食。

   nán​fāng​rén xí​guàn yǐ dà​mǐ wéi zhǔ​shí.

   Southerners are accustomed to having rice as their staple food.

   Source: Dong Chinese Dictionary

3. 米饭是中国南方人的主食。

   mǐ​fàn shì Zhōng​guó nán​fāng​rén de zhǔ​shí.

   Rice is the staple food for people in southern China.

   Source: Dong Chinese Dictionary