单项选择题 An graft is a surgical operation where a failing or damaged organ in the human body is removed and replaced with a new one. A.对B.错
单项选择题 COPD is a group of disorders characterized by airflow obstruction.A.对B.错
多项选择题 Suppose you want to promise that won’t happen again when making an apology, which of the following expressions can you use? ( )