单项选择题 Regarding to the electric dipole, which statement as follows is wrong? A、The electric dipole is composed of a positive charge of  and a negative charge of  , and the positive and negative point charges have separation  , and thus the dipole moment can be expressed as  B、The electric dipole is the name given to two point charges of equal magnitude and opposite sign, separated by a distance that is small compared to the distance to the point  at which we want to know the electric and potential fields. C、The potential arising from a point charge is inversely proportional to the distance  , while that of a electric dipole is inversely proportional to . D、The maximum magnitude of electric field is inversely proportional to .

单项选择题 在城市设计中抽象界线是作为条例、法律形式出现的。（ ）

单项选择题 下图属于哪种预均化堆场的布置方式？ A、圆形堆积 B、纵向堆积 C、环形堆积 D、锥形堆积