C) Tying the paragraph together is definitely one of them. If I had to choose another one I would include B) Emphasizing the important points.
Answer:
Ocean currents can be caused by wind, density differences in water masses caused by temperature and salinity variations, gravity, and events such as earthquakes or storms.
Answer:
<span>B. Singular subjects need singular verbs while plural subjects need plural verbs.
The agreement consists in that the number of the verb and the number of the subject need to be the same: if the subject is singular the verb has to be singular, and if the subjetc is plural the verb has to be plural.
Verb-subject disagreement is a grammatical error.
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