An expert in any field may be defined as a person who possesses specialized skills and is capable of rendering very competent services.

单项选择题Recent discoveries in Montana indicate that some dinosaurs may have resided in colonies.

单项选择题High wages and restrictive work practices are said to have created new nonunion competition.

单项选择题Among the men and women who reshaped the American working class during the early 1900s, there were many who were not members of labor unions.

单项选择题The most important result of the Lewis and Clark expedition was that it enabled the United States to claim the Oregon region.

单项选择题The cylindrical shape of a cactus reduces moisture loss.