westward expansion造句

Researchers are projecting a westward expansion of " Cactoblastis cactorum" in North America.

Winning by a narrow margin, Polk campaigned on his strong support for westward expansion, a hotly debated issue that was dodged by other candidates.

America's westward expansion went hard on the California sea otter, which seemed to vanish in the first half of the 19th century, an unlucky victim of the fur trade.