单项选择题 企业物流的合理化就是要降低成本、提高效率：其一，建立规范市场竞争机制，其二，是实现物流各环节作业的标准化 A、正确 B、错误

多项选择题 ()情况下,我们会采用高压高温合成

单项选择题 ‎A population distribution is normal with a mean of 18 and standard deviation of 4. A sample of 16 observations is selected and a sample mean computed. What is the probability that the sample mean is more than 18?‏