The accident happened __________20th September, 2008.[ ]
A. in
B. on
C. around
D. at
答案:B
Miss Zhao is very helpful. She often helps us ____we are in trouble.
A.whether
B.although
C.whenever
D.however
在突发事件的管理和应对中,隐性成本主要表现为信息失真成本和权威失灵成本。()