As a general rule, American men earn more than American women. This holds true across industries, across education levels, and across states. But, there's at least one big【C1】______: part-time employees. In 2012, women who worked less than 40 hours a week generally out-earned men who spent the same【C2】______at their jobs. If they worked 35 hours a week, they earned about 11 percent more. If they worked 25 hours a week, they earned about 4 percent more. But once females hit that magic 40 hour【C3】______their relative pay declined dramatically. So why do women beat out men while working part-time and【C4】______out while working full-time? My guess is that much (【C5】______certainly not all) of the explanation【C6】______down to two reasons: marriage and children. Women, including highly educated【C7】______, tend to cut their hours once they have families and children, especially【C8】______their husband has a higher salary. Men, meanwhile, are more likely to keep working a【C9】______week And so part-time women, as a group, are somewhat more likely to have gone to college, and【C10】______less likely to have dropped out of high school, than part-time men, who may well be working shorter【C11】______for lack of better options. The problem for women is that working part-time early in their careers can cost them salary while working full-time later in their careers,【C12】______lost experience and perhaps some【C13】______opportunities for promotions. Motherhood might be the most【C14】______job in the world. But all too often, our economy still makes it【C15】______a career killer. So【C16】______part-timers, which other women out-earn men? The BLS includes a job-by-job breakdown of the wage【C17】______, and among the nearly 150【C18】______with good-enough data to【C19】______, it found just two where females were better paid: counselors and health technicians. That said, as men look more toward those sorts of traditionally pink-collar jobs for employment, one has to【C20】______how long that pay advantage will last.

【正确答案】 D

【答案解析】解析：空格所在从句为表语从句，用于说明My guess，回答上句提出的疑问。但是作者所猜测的marriage and children这两个理由不可能完全解答这个问题。限定词much意为“很多，大量”，和空格后的all“全部”是相对的概念，存在让步转折关系。D项though意为“尽管”，表示让步，符合语义逻辑。