When a speaker responds to changes in circumstances by changing from one register to another during speech, s/he is engaging in what linguists call .

He is engaging in what is called Sociolinguiatics

(i can't select because there is no options but, i will answer) using evidence effectively. most of the assignments you will do in university will ask you to make an argument, to take a stance, or to prove a hypothesis. the best way to do this is to research the topic, develop a thesis statement, hypothesis, or claim and then use evidence to support this claim.

hello!

"hidesato showed not the least sign of fear. he tried to calm the dragon king: don't be afraid. i shall surely kill the centipede."

hope this .