What can be your Inspiration?
A、Collecting creative images
B、Architecture
C、Artwork
D、All of them

单项选择题In a steady electric field, the closed line integral of the external electric field intensity outside the power source is ______ to zero. The closed line integral of the Coulomb electric field intensity is ______ to zero. A、unequal, equal B、unequal, unequal C、equal, unequal D、equal, equal

单项选择题The famous Niagara Falls are located on the US-Canadian border ________.