渺渺和体育老师做一节课引体向上

　　Some five centuries ago, a major revolution overturned traditional ship design: in just a few years, ships were transformed from small coastal-bound transports into massive ocean-going vessels. Once regular trans-oceanic travel became feasible, everything changed. 　　Powerful navies arose and fought for supremacy at sea, while the new ships enabled empire-building European powers ... (展开全部)