↓ここからが創作問題 「妹は帰宅してからずっと、数学の勉強をしている」 My sister has been studying mathematics since she came home. (以下、日本語省略) I have been studying English since I came home. We have been studying French since we came home. We have been studying French since we finished our lunch. They have been studying French since they finished their lunch. She has been studying French since she finished her lunch. They have been dancing since the concert started.