Option 1: Bay- This refers to a body of water partially enclosed by land. It is typically larger and more open than a strait, and does not connect two seas directly. Therefore, this option is not the correct answer.

Option 2: Peninsula- This refers to a piece of land that is surrounded by water on three sides but still connected to a larger landmass. It does not involve a narrow stretch of water connecting two seas, so this option is not the correct answer.

Option 3: Isthmus- This refers to a narrow strip of land that connects two larger land areas. It does not involve water and does not specifically refer to connecting two seas, so this option is not the correct answer.

Option 4: Strait- This is the correct answer. A strait refers to a narrow stretch of water that connects two larger bodies of water, such as seas or oceans. It is often formed by the movement of tectonic plates or erosion, and acts as a passage between two bodies of water. Examples include the Strait of Gibraltar and the Strait of Hormuz.