题目

The president was __________ a speech to senators __________ a group of armed young people burst into the hall A . giving; as B . making; when C . delivering; while D . speaking; when 答案：B19．若等差数列{an}的公差为d，前n项的和为Sn，则数列{$\frac{{S}_{n}}{n}$}为等差数列，公差为$\frac{d}{2}$．类似，若各项均为正数的等比数列{bn}的公比为q，前n项的积为Tn，则等比数列{$\root{n}{{T}_{n}}$}的公比为（　　）A．$\frac{q}{2}$B．q2C．$\sqrt{q}$D．$\root{n}{q}$