题目

    In US, the potato is one of the most widely consumed crops．French fries are commonly found in typical American fast-food burger joints and cafeterias．French fries were introduced to the US when Thomas Jefferson served them in the White House during his presidency from 1801 t0 1809．Potato chips are popular with consumers as well．    The humble potato is more than just a kind of food．In many ways it's part of the American pop culture．Let's take a look at some pop culture potatoes．     Mashed Potato dance        The Mashed Potato dance is a craze that be关于生长素的作用，下列说法正确的是 A．未用生长素处理过的植物枝条扦插后是不能成活的    B．生长素的浓度越高植物生长越快 C．发育着的种子能产生大量生长素，为子房发育成果实提供必要条件 D．侧芽产生的生长素比顶芽多，所以侧芽的生长受到抑制