问题探究 
自19世纪中叶起，西方列强挟坚船利炮，先后对中国发动多次侵华战争。清政府被迫同列强签订了一系列不平等的条约，中国领土主权屡遭破坏，一步一步陷入半殖民地半封建社会的深渊。中华民族为反抗侵略，进行了不屈不挠的斗争。据此回答下列问题：

古人称黄河水是“一石水，六斗泥”．创意中学综合实践小组从黄河中取了2×10^﹣3m³的水，称得质量为2.2kg，由此可知含泥沙的黄河水的密度为____kg/m³．一条货船在黄河中航行时，浸在水中的体积是30m³．船受到的浮力为____N．在码头将货物卸下后，河水对船底压强大小的变化情况是____（本题g取10 N/kg）．

   Everybody knows vegetables and fruit are g____for people．Many people eat some fruit each day．Mr and Mrs Smith like e____ fruit very much and every day Mrs Smith goes to buy some fruit in the shop near her home. She can buy all k____ of fruits there，such as apples，pears, oranges and bananas．In different time of the year the p____ of each kind of fruit is not the same，s____  high，sometimes low. Mrs Smith usually t____  to buy cheap fruit．And b____  are Mr Smith’s favourite fruit．Mrs Smith buys bananas for him every week．But she always chooses the cheap ones.“Eating fruit can help to keep f____ ，" said Mr Smith．“It's quite d ____ from snacks．Both of them can give us energy．But snacks l____ cakes, chocolates and sweets are not good for our health at all,"