人误服重金属盐中毒后．为了减轻毒性．可服用下列物质中的（   ）

____(tell) many times, he still repeated the same mistakes.

如图所示，L为理想变压器，其原线圈、副线圈的匝数分别为n₁ n₂ ④为理想交流电流表，阻值分别为R、r的两个定值电阻接在电路中．将a、b两端接到电压恒定的交流电源上，当开关S分别拨至接线柱l和2时，发现电流表的示数相同．则两个定值电阻的阻值之比r/R等于(   )  

Just 10 percent of the 30 million Chinese currently suffering from depression are getting proper medical care _____ a lack of enough healthcare and social prejudice against mental illness, experts have said.

计算．

$\left(\frac{\text{1}}{\text{2}}-\frac{\text{1}}{\text{4}}\right)\times \frac{\text{4}}{\text{5}}+\frac{7}{10}=$ ____