Could you tell me which one is right among the following sentences?<br/>Thank you.<br/><br/><b>(A1) What is most difficult <u>about learning English</u>?</b><br/><b>(A2) What is most difficult <u>in learing English</u>?</b><br/><b>(A3) What is most difficult <u>to learn English</u>?</b><br/><br/><b>(B1) Do you want to explain it in English <u>for your understanding</u>?</b><br/><b>(B2) Do you want to explain it in Englsih <u>to better understand</u>?</b>