Final answer:
Reading a variety of books is the most effective activity for enhancing students' expressive vocabulary, and actively engaging with the books by keeping a reading journal reinforces vocabulary acquisition. Complementary writing essays also provide practical application of new words.
Step-by-step explanation:
If a teacher wants to work on students' expressive vocabulary, the most effective activity would likely be reading a variety of books. Reading exposes students to new words and usage in context, which can significantly enhance their vocabulary. Moreover, actively engaging with the text through methods such as a reading journal can reinforce understanding and retention of new words. Writing notes, summarizing plots, asking questions about the text, and recording quotes with in-text citations are all strategies that can support vocabulary development. Additionally, writing essays can be a complementary activity, as it offers an opportunity for students to apply their expanded vocabulary in practice. Therefore, prioritizing the writing process, while also encouraging extensive reading, can lead to efficient and effective vocabulary building.