Which of the following statements about surface waves is true?
1. surface waves are caused by winds.
2. surface waves can travel at 950 kilometers per hour.
3. surface waves are caused by underwater earthquakes.
4. surface waves have a longer wavelength than tsunami waves have.

Many organizations release indexes used to measure the development of the world's countries. as we learned in this lesson, these indexes measure many factors, from life expectancy to happiness. in your opinion, what are the three most important factors we can use to determine how developed a country might be? explain your answers in a few sentences.