Today is Saturday. The weather is warm and sunny. Bob and Jack go to the park. There are many people there. The girl under a big tree is reading a book. Two boys are playing football on the grass. The girl in a red dress is riding a bike. Two women are talking. The man beside these women is playing with a baby. Bob and Jack are beside the river. They are sitting on the chair and drawing pictures.

如图所示，长为L，高为h，质量为m的小车停在光滑的水平地面上，有一质量为m的小物块（可视为质点），从光滑曲面上离车顶高度为h处由静止下滑，离开曲面后水平向右滑到小车上，最终物块滑离小车．已知重力加速度为g，物块与小车间的动摩擦因数μ= $\frac{4h}{9L}$ ，求：

①让行司机洋溢着高度的文化自觉和文化自信

②让行司机是中华文化的传播和交流的使者

③让行司机是中华民族传统美德的继承者和发扬者

④让行司机为培育文明风尚身体力行

我国民间有许多传统的食物，如“腊八粥”、“鱼肉粥”“荤素饺”等．从营养学的角度看，这些食品的共同特点是（    ）