Why don't students guess? I have been on italki for less than a month, but I see endless questions asking if the answer is A or B. The student usually never says what he/she thinks the answer is. Imagine if a student actually guessed each one of their questions and discovered that they got a very high percentage correct, or perhaps ALL of them! Maybe they would gain some confidence and move forward with their language learning instead of questioning every doubt. In addition, it is helpful to the answerer to explain if the asker got the guess wrong. If the asker guessed correctly, there is no need to even answer the question, as the lack of an answer could signify a correct guess. By the way, I have a Master's degree in  teaching English as a Second (foreign) Language and over 15 years of teaching experience, so I have seen what fear of failure can do to students. Anyway, my rant. Just try.