【单选题】

Questions 18 to 20 are based on the following passage.At the end of the passage, you will be given 15 seconds to answer the questions.

Now, listen to the passage.
What does the speaker say about the ocean’s level of saltinessA．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, which leads to a rise in oceanic salinity level.
D．Salt has accumulated very quickly at the early stage of life formation, then this process gradually slow down.