💡 Detailed Explanation
The correct choice is 'せ' (causative form indicator for Group 1 verbs). The verb '書く' (kaku - to write) conjugates to its causative form '書かせる' (kakaseru) by changing the 'u' sound to 'a' and adding 'せる' (kaka + se + masu). Sentence translation: 'The strict teacher makes the students write many essays every day.' 'させ' is the causative suffix for Group 2 or irregular verbs (e.g. 食べさせる, させる), while '書く' is Group 1. 'まれ' and 'られ' are passive indicators.