600点 文法問題 接続・前置詞 invest in TOEIC Part 5 練習問題 P5_517 The company has invested heavily ------- research and development. A. in B. for C. to D. at ✅ 正解:in ✅ 正解根拠:invest in。 🎯 秒解きポイント:invest=in。 文法問題 接続・前置詞 invest in