Why did the u. n forces ( mostly Americans ) get pushed back across the 38th parallel

Because Communist China entered the war on North Korea's side.

Explanation:

However, as the Americans moved north toward the Yalu River, the border between North Korea and Communist China, their advance was halted when China entered the fray that fall. In late November, a massive force of Chinese troops sent the Allies into retreat. In early January 1951, the Communists recaptured Seoul, only to have the Allies reoccupy it in March.

Mark me brainliest if I helped:D

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.