在实际检索中，文献的检索方法主要有：直查法、（）、（）和综合法。
参考答案：追溯法;工具法
---- What was it that made Susan weep?
---- ________of cheating in the exam.
A．Being charged
B．That she was accusing
C．Because she was charged
D．Being accused
规整填料塔与筛板塔相比有什么优点？
