What are the important things i learned from the text

the heading: the heading can include your address and the date. in casual, friendly letters your address is not necessary.
the salutation (greeting): this usually begins with the blank is for the name of the person you are writing. after you write the person's name you put a comma ( , ) .
the body: the body of the letter is the information you are writing in your letter.
the closing: in the closing the first word is capitalized and you put a comma after the last word.
some examples of closings are:

sincerely,
your friend,
love,
very truly yours,
5. your signature: this is your name. it goes under the closing

answer:

polluted water, i know a river who is dirty it is pasig river but i dont know anything about different sea