Cuando se utiliza -at- en prepocion

They indicate the position of something or someone, relative to something else. Examples of prepositions include: in, on, above, underneath, through, across, with, near, between. Interestingly, prepositions are known as a “closed” word class. Unlike nouns and verbs, no new ones will be added over time.

ok

Explanation:

¿Con qué necesitas ayuda? Hay una pregunta, si es así, ¿Qué es gracias?

The correct answer is an appeal to logic.
In his speech, Mandela proves logically why all people deserve respect and equality. He does not appeal to emotion but rather to logic. Nor is he using figurative language: he is stating the facts, plain and simple. He uses evidence and reasoning to prove his point.
if you have questions message me for how i got the answer