单项选择题Pendulums are used to regulate motion in some scientific equipments.
单项选择题Manufacturers spend millions of dollars on advertising to entice people to buy their products.
单项选择题The painter Les Quinones, whose graffiti art has been exhibited in New York galleries, has also painted outdoor murals in various Manhattan neighborhoods.
单项选择题The North American desert, a vast belt of inhospitable terrain, stretches erratically down the western side of the continent.
单项选择题Today in the United States, adult education facilities face rising demand created by expanding leisure time.