ADMICRO

Read the passage below carefully, and then choose the best answer:
Ocean Currents and the Turning of the Tide
If you take a seat at the beach and look out across the water, you’ll soon notice that oceans have a rhythm of their own. Throughout the course of the day, sea levels will rise and fall, and water will flow through routes and end up in different places. But how does it all work? One force at play is tides, which are the alternating water levels of the ocean. There are two major gravitational forces which cause tides: the sun and the moon. The moon’s force has a tugging effect on oceans which causes them to bulge outwards on opposite sides of the planet. Solar tides operate according to the same principles. However, they are only about 50 percent as strong due to the distance between the sun and the earth. As tides rise and fall, they create tidal currents. The strongest tidal currents occur at the height of both high and low tides. Unlike other currents, they do not flow in a continuous stream. Far from shore, tidal currents don’t have much of an effect. Yet when they pass through narrow area, like harbours and bays, tidal currents can displace plants, animals, and sediment. Although they may certainly shake things up, not all of the damage is negative. Tidal currents can spread fish eggs across long distances to assist fertilization, in addition to transporting key nutrients. Another category of currents is ocean currents. These currents occur near the top of the water, and are mainly powered by the wind. One example of these is coastal currents, which are those beachgoers encounter when going for a swim. One of the strongest and most well-known currents is the Gulf Stream, which brings warm water from the Gulf of Mexico all the way to Western Europe. Meanwhile, Deep Ocean currents are a powerful force in the depths of oceans. The strongest of these has been nicknamed the global conveyor belt, and it moves much slower than surface currents. Although we can’t see it in operation, it’s about 16 times as powerful as all the earth’s rivers put together. As the global conveyor belt pushes water around the planet, it carries nutrition and carbon dioxide to places that truly need them. In the end, although there are several currents working on oceans simultaneously, they each seem to perform a necessary function that creates balance for life in the sea.
1. How do moon tides different from solar tides?

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