动态心电图判断抗心律失常药物疗效通常采用ESVEM标准，判定对短阵室性心动过速治疗有效的标准是（）。

A.减少≥50%

B.减少≥60%

C.减少≥70%

D.减少≥80%

E.减少≥90%

Marko Tskitishvili, an economist, has been studying the drop in the price of the average household computer in the U.S. and wonders if computers should still be considered a luxury good or if it has now become a normal good. He conducts a survey of 500 people and finds the following:

Assume that 1998 is the base date. Based on the above data, Tskitishvili would conclude that a computer is a:（）

A. luxury good with income elasticity of 1.01.

B. normal good with income elasticity of 0.84.

C. luxury good with income elasticity of 1.18.