油气润滑是（）与润滑的润滑方式。
A.液化气
B.压缩空气
C.混合空气
D.天然气
参考答案：B
关系R、S如下图所示，关系代数表达式π3，4，5(σ1＜6 (R×S))=(63)，对关系R、 S进行自然连接后的属性列数和元组个数分别为 (64) 。
Which of the following is a company least likely required to present according to International Accounting Standard (IAS) No. 1（）
A. Cash flow statement.
B. Disclosures of material events.
C. Statement of changes in owners' equity.
