题目

Some people will do just about anything to save money. And I am one of them. My family’s last vacation was a good    1    to prove it. It was my six-year-old son’s winter break from school, and we were    2    home from Fort Lauderdale after a week-long trip. The flight was    3   , and Delta, the airline, offered us $400 per person in credits to give up our seats and leave the next day. I had meetings in New York, so I had to    4   . But that didn't mean my husband and my son couldn't stay. I took my nine-month-old and took off for home. The next day, my husb如图，△ABC内有一点D，且DA=DB=DC，若∠DAB=20°，∠DAC=30°，则∠BDC的大小是                                                              【     】 A.100°           B.80°               C.70°              D.50°