💡 Detailed Explanation
The correct choice is 'にくい' (difficult to do). The grammar pattern '[Verb Stem] + にくい' expresses that performing an action is difficult or troublesome. Sentence translation: 'Because this textbook has a lot of kanji, it is a bit difficult to read.' 'やすい' means easy to do. 'はじめ' means start doing. 'すぎ' means to do excessively.