罗杰斯的“以学生为本”、“让学生自发学习”、“排除对学习者自身的威胁”的教学原则属于( )。

单项选择题Whether by accident or ______, he arrived too late to help us.

单项选择题—Who's won the first prize in the competition —Henry ______. He has ______ it for a week.

单项选择题—______ Your name again, please. —It's Bell Green.

单项选择题—I'll be away on a business trip. Would you mind looking after my pet dog —______.

单项选择题—When was the first man with A(H1N1) flu in mainland China known for sure —______ May 11, 2009.