Preposition = 前置詞 以下の文章に前置詞をつけて見ましょう！
(1) The flight from San Francisco will arrive ___ 14:20.
(2) I went shopping ___ Friday.
(3) We can see autumn leaves in Japan every year ___ November.
(4) Christmas is ___ December 25th.
(5) I have a big breakfast ___ the morning everyday.
できたのかな？
正解は：
(1) The flight from San Francisco will arrive _at_ 14:20.
(2) I went shopping _on_ Friday.
(3) We can see autumn leaves in Japan every year _in_ November.
(4) Christmas is _on_ December 25th.
(5) I have a big breakfast _in_ the morning everyday.
回答：
"at" = used for time / 時間に使われる
"on" = specific day / 決められた日にち
"in" = general day or time (we don't know specifically which day in November nor specifically what time in the morning) / 決められていない日にち・時間（１１月の何日か、朝の何時か話の中で確定していない）
Hope this helps!
変な日本語があったらごめんね！
See you!
