There is a red apple on the desk. [Syntax]

The correct answer is "が" (ga). This particle marks the subject of existence when using verbs like "あります" (arimasu, to exist/be for inanimate objects) or "います" (imasu, for animate objects). It indicates what is present. "あかい" (akai) is an adjective meaning "red," which describes "りんご" (ringo, apple). "りんご" is the noun that exists. "あります" is the verb for existence, which comes at the end of the sentence.

正解は「が」です。「あります」や「います」と一緒に使われ、何が存在するかの主語を示します。「あかい」は形容詞で「りんご」を修飾します。「りんご」は存在する名詞です。「あります」は文の最後にくる動詞です。