Americans’ (1) impulses keep generating surprises. Charitable giving plays an even larger role in the (2) . Demand for nonprofit services gets proportionately bigger as a locality’s (3) rises. The philanthropy of the wealthy may not hinge on tax (4) to the degree many believe. The US (5) the world in levels of charitable activity. Some experts see charity as a (6) trait of the US, more than (7) or business. But those forces may be (8) , as many nonprofits, from healthcare to classical music are selling (9) in a marketplace alongside for-profit (10) . Charity is no mere (11) activity. It pays off for society in ways that may (12) the rates of return on many traditional investments. Charity not only helps those on the (13) end but also strengthens the (14) of society at large. Moreover, it appears to make the givers themselves more (15) . The pattern that conservatives are better givers than (16) is less about politics than about charity-linked (17) most common to conservatives, religious commitment, marriage and children, and entrepreneurship. The main point is that more Americans, regardless of ideology, embrace giving as a tool for (18) . The urge to make a difference, and to take (19) in it, outweighs (20) considerations.
可知此场中某点的电场强度E与F成正比
可知电场中某点的电势φ与q成反比