Read the passage. I left the port city early in the morning. The boat was loaded with wood, spices, and perfumes from lands acro
ss the sea. Raising our sails, we caught the wind and sailed the mighty Nile. At one market, I bartered for more linen and grains. At another, we obtained oil and wine. At the next, salt. Yes, we needed that. I watched another merchant amble away, his donkeys pulling carts filled with jars and bundles. I had farther to go, too. I thanked the river for speeding my journey. Its waters were low, and I watched workers turning lumber like ours into new boats along its banks. In a few days, we would reach Aswan. There, we would trade for gold and animal skins. Perhaps we would find new things, too, before turning around and beginning the trip anew. What was the importance of the Nile River as described in this passage? The Nile River was used to transport many trade goods. Only non-food goods could be transported on the Nile River. People relied only on the current of the Nile River to move their boats. The Nile River was used for transportation when the water was at its highest.
The answer to the item above is letter "C. surface". Surface waves are mechanical waves that propagate in the interface of differing media. These waves very usually have larger altitudes and longer wavelengths than the body waves.
