如图所示的电路中，电压U不变，开关S断开后，下列说法正确的是：

搜题请搜索小程序“爱下问搜题”

问题选择题

[ ]

A．电压表的读数减小

B．电压表的读数增大

C．电流表的读数减小

D．电流表的读数增大

答案

答案：C

解答题

4x-1=0既是等式，也是方程．______（判断正误）

查看答案

单项选择题

Mud from a lake on an uninhabited wooded island in northern Lake Superior contains toxic chemicals, including toxaphene, a banned pesticide for cotton that previously was manufactured and used, not in nearby region of Canada or the northern United States, but in the southern United States. No dumping has occurred on the island. The island lake is sufficiently elevated that water from Lake Superior does not reach it.
The statements above, if true, most ply support which of the following hypotheses

A．The waters of the island lake are more severely polluted than those of Lake Superior.

B．The toxaphene was carried to the island in the atmosphere by winds.

C．Banning chemicals such as toxaphene does not aid the natural environment.

D．Toxaphene has adverse effects on human beings but not on other organisms.

E．(E) Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient to be measurable.

查看答案