What is the disadvantage of wave energy according to the passage?

* Hướng dẫn giải

Dẫn chứng: However, there is the challenge of converting wave power into energy and transmitting it to shore. Building and operating wave power stations in the ocean is far more expensive and difficult than on land. Also, salt water is a very hostile environment to devices. They go rusty easily and cannot last as long as those on shore. Sea waves make energy harvesting even harder by moving up and down most of the time.