题目

Data collected by the World Food Program shows that every year over 847 million people worldwide suffer from malnutrition and about 3.1 million children under the age of 5 die of starvation.While dealing with world hunger is an important thing for scientists, it is not easy, considering natural resources. But thanks to new ideas like Livingbox, there may be some hope.The Israeli scientists Nitzan Solan and Moti Cohen say Livingbox is an environment-friendly ecosystem made of some connected boxes to form a mini-farm. This means that the vegetables are grown in water instead of soil.While profes如图所示,为使带正电小球平衡于图示位置,可在以小球为圆心的圆周上的相关区域固定另一电荷。若小球电量始终不变,则下列说法正确的是( )A. 可在AB区域固定负电荷，且自A至B电荷量应逐渐增大B. 可在BCD区域固定负电荷，且自B至D电荷量应先减小后增大C. 可在BC区域固定负电荷，且自B至C电荷量应先增大后减小D. 可在AD区域固定正电荷，且自A至D电荷量应先减小后增大