下列有关log-rank检验的描述中正确的是

A:log-rank检验是各组生存率的整体比较 B:log-rank检验是各组生存率各个时间点的比较 C:log-rank检验近似法较精确法保守 D:log-rank检验中，各组实际死亡数之和必等于理论死亡数之和 E:log-rank检验的自由度为（组数-1）

The product was processed ( ) official veterinary supervision.

A:in B:under C:after D:with

The following answer is ( ) to official confirmation.

A:to subject B:subject C:subjected D:subjecting

The following answer is ( ) to official confirmation.

A:to subject B:subject C:subjected D:subjecting

______是“Web Log”的缩写。

A:Blog B:播客 C:网页 D:邮件

已知${\log }_{2}a>{\log }_{2}b$，则下列不等式一定成立的是（ ）

A:$\frac{1}{a}>\frac{1}{b}$ B:${\log }_2\left(a-b\right)>0$ C:${\left(\frac{1}{3}\right)}^a<{\left(\frac{1}{2}\right)}^b$ D:$2^{a-b}<1$