专四专八考试

【单选题】
What does the speaker say about the ocean’s level of saltiness
A、The level of saltiness in the ocean is extraordinarily high.
B、The average level of salinity in the ocean is higher than that of inland lakes.
C、Salt has been gradually accumulating in the ocean.
D、Salt has accumulated very quickly at the early stage of life formation.
网考网参考答案：C
网考网解析：
[听力原文] Scientists believe that when the oceans were young, they contained only a trace of salt, and that the level of salinity has been going up gradually. Over the years, rains have been wearing away the rock mantle of the continent. Minerals released by the erosion have been carried to the sea by the flow of river water. This water adds several billion tons of salt to the ocean annually. There are other sources of oceanic salinity too. One source is underwater volcanic action. These eruptions occur along the mid-ocean ridge and release great amounts of salt into the sea each year. However, these sources don’t increase the actual mineral composition of the water by much because of the enormous chemical requirements of marine life. Oysters, clams, mussels and other mollusk use salt to build shells and skeletons. Coral reefs also consume large amounts of salt. Also, some salt leaves the ocean through the process of evaporation. As salts escape into the atmosphere, they go into the creation of rain drops. This is why the coast receives more rain. Salt exists in the atmosphere near the ocean, thereby attracting the increased moisture and producing rain. 本题出题点在短文开头。短文开头处提到了海洋盐度的问题，讲到海盐是慢慢积聚起来的，故选C。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>