常见的转折关键词有：believe,argue,contend, Claim,theorize,assert,view, announce,etc.
在申友第5版讲义第17篇，p148文章首句，就以believe引出了观点。 Many people believe that because wages are lower in developing countries than in developed countries, competition from developing countries in goods traded internationally will soon eliminate large numbers of jobs in developed countries.
The view has prevailed for the better part of the twentieth century that small firms do not perform an important role in Western economies.
Thus, an alternative view has emerged in the economics, arguing that small firms make several important contributions to industrial markets.
The Black Death, a severe epidemic that ravaged fourteenth-century Europe, has intrigued scholars ever since Francis Gasquet's 1893 study contending that this epidemic greatly intensified the political and religious upheaval that ended the Middle Ages.
In the 1930s, however, Evgeny Kosminsky and other Marxist historians claimed the epidemic was merely an ancillary factor contributing to a general agrarian crisis stemming primarily from the inevitable decay of European feudalism.
同样第12篇， In arguing that this decline of feudalism was economically determined, the Marxist asserted that the Black Death was a relatively insignificant factor.
Many scholars have theorized that economic development, particularly industrialization and urbanization, con-tributes to the growth of participatory democracy.
Two years later, the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars.