As shown in the figure, it shows a daily variation curve of land and ocean surface temperature in coastal areas. Read and answer the questions 18 ~ 19. The above description is correct (

A, the sea water temperature is low during the day and the land temperature is high at night. Therefore, ① in the picture is land, so it does not meet the meaning of the question;

B, the sea water temperature is low during the day and the land temperature is high at night. Therefore, ② in the picture is the ocean, so it is correct;

C, the temperature difference caused by the figure is mainly caused by their different specific heat capacity, rather than the length of day and night, so it does not meet the meaning of the question;

D, the temperature difference in the figure is mainly caused by the difference of their specific heat capacity, not by latitude, so it does not meet the meaning of the question.

Therefore, choose: B.