The correct answer is 1. language learner because risk-taking is an essential trait for acquiring a new language effectively. Here's why:
Language learners need to take risks by speaking, writing, and experimenting with the language, even if they make mistakes. This willingness to step out of their comfort zone helps them improve and gain fluency.
A language teacher (option 2) should encourage risk-taking in students but does not necessarily need to be a risk-taker themselves.
A teacher of grammar rules (option 3) focuses on accuracy and correctness rather than taking risks.
A printer of books and authors (option 4) has no relation to risk-taking in language learning.
Thus, the best answer is 1. language learner because taking risks is crucial for effective language acquisition.