The key idea of the text is that friends are important because they

they help us through tough times and are always there to back us up or tell us when we need let loose

Have our back if and when we need them no-matter what, can put rumors behind them because you shouldn't believe in what other people say that your friends said if he/she is your true friend believe in him/her, not other people who could be jealous.

Explanation:

mi hermana "sabe" bailar salsa. "conoces" tu el monumento la mitad del mundo? raul y yo sabemos al profesor de matematicas.

translated: my sister "knows" how to dance salsa. "do you know" the monument half of the world? raul and i "know" the math professor.

answer; /// the correct answer to the above statement is (a) because of the decline on native american labor forces;