If you get a bad score on your test, what do you plan to say to the teacher if he/she asks you what you were doing today?
ご質問ありがとうございます。
"If you get a bad score on your test,"＝「もしテストで悪い点を取ったら、」
"what do you plan to say to the teacher"＝「先生に何て言うつもりなの」
"if he/she asks you what you were doing today?"＝「君が今日何をしていたかと聞かれたら。」
ご参考までに。
アメリカ合衆国 
