回答
The child must be kind to give up his seat to an elderly person on the train.
My brother said to me that I should study hard when I’m in high school.
ありがとうございます！！
My brother said me that you should better study English hard when you are high school students.
ありがとうございます！
疑問は解決しましたか？
この質問を見ている人は
こちらの質問も見ています😉
the elderly で高齢者(名詞的)
an elderly person でも高齢者 (形容詞的)