题目

— Mary, this is my sister Kate. — _____________ — Nice to meet you, too!A. How are you?      B. Good morning!    C. Nice to meet you!     D. Bye! 答案：C(本题满分10分) ⑴如图，已知∠AOB=90º，∠BOC=30º，OM平分∠AOB，ON平分∠BOC，求∠MON的度数；⑵如果⑴中∠AOB=α，∠BOC=β（β为锐角）,其他条件不变，求∠MON的度数；⑵ 从⑴、⑵的结果中能得出什么结论？