你知道世界上最受欢迎的饮料——茶是由于意外而发现的吗

单项选择题Who brought the writer the bad news that her mother was ill ______

单项选择题Hollywood used to be a ______.

单项选择题What made Professor Broad continue his search for more information on McKay

单项选择题（1）（）

A．applying
B．doing
C．offering
D．getting

问答题请简要回答研究性学习的含义及其本质。