题目

It has been proved _______ eating vegetables in childhood helps to protect you against serious illnesses in later life. A. if          B. that     C. what      D. when 答案：B 解析: 略一艘轮船从河里航行到海里，船露出海水外的体积将    ，受到海水对它的浮力的大小     （填：增大、减少或不变）．