C. a refrain, because it's a point of emphasis
(essential, crucial, required, needed, important) pick whichever one is in the parenthesis as i can’t see the text that you’re reading
You can find some useful tips via the Internet. Try to describe your friendship by one word and. I think you should write the most interesting events with you and your friends. Write why do think he's your best friend. But you should focus on interesting things. So it would be good if you write something funny about you and your friend.
"response variable", "regressand", "predicted variable", "measured variable", "explained variable", "experimental variable", "responding variable", "outcome variable", "output variable" or "label".
it all depends on the context :)
