a warship that can operate both on and under water
潜艇, 潜水艇
潜艇在第二次世界大战期间的海战中发挥了关键作用，扰乱了敌人的补给线。
a type of small vehicle that is used to travel on water
船, 小船
beneath the surface of a body of water
水下, 水下的
潜水员通过在水下停留近一个小时来探索珊瑚礁。
to visit places one has never seen before
探索, 发现
the vast body of salt water that covers most of Earth's surface
the armed forces of a country
军队, 武装力量
a flat part of a bicycle or machine that is pushed with the foot to make it move or operate. It is typically circular and part of the mechanism that drives motion
踏板, 脚蹬子
我自行车上的踏板松了，需要拧紧。
a machine that uses steam made from boiling water to produce power and make parts move
蒸汽机, 蒸汽发动机
蒸汽机帮助开始了工业革命。
a state of armed fighting between two or more groups, nations, or states
战争
the war that took place from the year 1914 to 1918 between the allies and the central powers
第一次世界大战
the war that took place from the year 1939 to 1945 between the axis and the allies
第二次世界大战, 二战
to act violently against someone or something to try to harm them
攻击, 袭击
a country or its forces that one is fighting against in a war
敌人, 对手
a device that produces electricity; may have several primary or secondary cells arranged in parallel or series
电池, 蓄电池
newly developed and incorporating new, modern methods or technology
先进的, 创新的
他们应用了先进的算法来提高数据处理速度。
a type of energy generated by splitting atoms to release their stored energy
核能, 核动力
该国正在投资核能以减少对化石燃料的依赖。
to prevent someone or something from being damaged or harmed
保护, 防护
someone whose job or education is about science
科学家, 研究员
the earth's surface where it is not under water
土地, 地面
to keep something in a particular place for later use, typically in a systematic or organized manner
储存, 存放
