可爱的猴子

    Look at those monkeys! How lovely they are! A mother and a baby are sitting on the hill. The mother is talking to its child. Some monkeys are jumping up and down. Others are swinging. I throw some bananas to them. One of them gets a banana. It runs away quickly and eats the banana behind the hill. I take photos of them. Suddenly I find two of them picking up stones. What do they want to do? Ha! They are talking photos, too.

一根两端开口、粗细均匀的长直玻璃管横截面积为S=2×10^﹣3m²，竖直插入水面足够宽广的水中．管中有一个质量m=0.6kg的活塞，封闭一段长度L₀=66cm的气体，如图．开始时，活塞处于静止状态，不计活塞与管壁间的摩擦．已知外界大气压强p_o=1.0×10⁵Pa，水的密度ρ=1.0×10³kg/m³，重力加速度g=10m/s²．求：

               是我国社会主义经济制度的基础。（     ）

下列方程中，是一元一次方程的为（　　）