如果abcd <0，a +b= 0，cd>0，那么这四数中，负数的个数至少有[ ]
A. 4个
B. 3个
C. 2个
D. 1 个
D
— What are the students ________ about?
— Whether Senior 3 students should join in the coming school sports meet.[ ]
A. quarrelling
B. inspiring
C. fighting
D. arguing
布鲁纳认为学习包括获得、转化和（）三个过程。
