氧化锡是一种对气体中酒精含量敏感的材料：当周围气体中酒精浓度发生变化时，其阻值也会发生变化．小明为研究某型号氧化锡检测电阻咫的阻值随气体中酒精浓度变化的关系，采用题图1所示实验装置进行实验：在可以直接测得酒精浓度的容器中喷入雾状酒精，闭合电路，调节滑动变阻器的阻值至适当值，读出电压表和电流表的示数，改变喷入雾状酒精的量，重复上述实验，计算出风的值．即可得到电阻的阻值随气体中酒精浓度变化的关系图线．

（1）每次实验之前，小明都应先将滑动变阻器R的滑动片置于______端（选填“a”或“b”）：

（2）小明在实验中测得多组数据如下表所示：

（3）我国《道路交通安全法》规定：严禁酒后驾车!参照《车辆驾驶人员呼气酒精含量阈值与检验标准（GBl9522）》，呼气中酒精浓度大于等于0.09mg/L就属于酒后驾车．小明用该型号氧化锡检测电阻R制成一个简易的酒驾测试仪．给定下列器材和要求，请你在题图3中帮他连接实物图；

器材：电源（E=6V，r=2Ω）、开关S、氧化锡检测电阻R_x、定值电阻R₀、理想电压表、导线．

要求：闭合开关S，检测者呼出气体流经Rx．若电压表读数大于等于1.2V，则检测者属于酒后驾车；若电压表读数小于1.2V，则不属于酒后驾车．

（4）在（3）问中，定值电阻R₀的阻值应为______Ω．

A patrol team of sea lions and dolphins featured in a large-scale military exercises being conducted by the U. S. and its allies in the Pacific Ocean. The machine (1) took part in simulated mine recovery and mine detection missions during the biennial Rim of the Pacific Exercise (RIMPAC) war games. The (2) started on June 19 and will run (3) Friday.
"There are a number of mechanical systems that work in those areas. (4) high-tech gadgets deployed by the military can’t (5) the natural skills of dolphins and lions," said Tom Lapuzza, spokesman for UN Navy’s Marine Mammal Program. Sea lions have "incredible good underwater (6) " and can dive down to 300 meters to catch a recovery line to a mine, he said. Dolphins use sonar to (7) mine.
Human beings have a long (8) of training animals to join the military. Horses have been the most widely-used animals (9) the recorded history of (10) . In early times, horses were used to (11) chariots or to (12) armored forces. With the development of modem weapons and motorized (13) , the use of horses for military purposes fell into (14) . (15) , horses were still used (16) by the German army during World War II for transporting (17) and equipment, including artillery.
During World War II, (18) with explosives strapped to their backs were used as anti-tank weapons. In other (19) , they were used for detecting mines. Some dogs were also used as messengers.
Other animals have also (20) in the military. Recorded history shows the use of elephants for military purposes as early as 1,100 B. C.. They were employed during World War II by both the Japanese army and the (21) .
There are records showing that over 100,000 reindeer were used by Finland to tow sleds during World War II. They carried the (22) to hospitals, brought supplies to the troops and moved heavy anti-tank weapons. It is well documented that oxen have been (23) used in war as improvised beasts of burden. During World War II, spiders were employed by the Allies to spin silk for (24) in cross-hairs on bomb scopes and other optical instruments. People also are finding that Vampire bats’ ability to use echolocation is very interesting as we (25) to learn how it works and it may benefit the army.