C. Write a letter to the editor describing the problem of pure drinking
water.
[5

Dear Editor, pure drinking water is scarce

Explanation:

this would be in the imperative mood. it is a category of verb forms that are used to express orders,instructions,commands or requests.

an argumentative essay presents objectively a topic and its main characteristics. besides, it states all this information and facts by giving authentic and substantiated proof to the audience. by contrast, a persuasive text purpose is to convince the audience about some facts by presenting them according to his/her emotions and feelings. the main purpose of a persuasive text is to convince the audience to agree with the author´s opinion. on the other hand, in the argumentative essay, the author leads the writer to recognize his/her point of view as the correct one.