题目

阅读理解 Sitting among a sea of cars, have you ever dreamed about your car taking off and flying over the road? Many of us spend an hour or so stuck in traffic every week. The main problem is that we are not expanding (扩展)our transportation systems fast enough to meet ever increasing demands (需求). One solution is to create a new type of transportation that doesn't rely on roads. In the last century, planes and cars changed the way we lived. Cars, which can be afforded by the general population，have allowed us to move farther. Planes have also cut travel time to faraway destinati25℃时，在某物质的溶液中，由水电离出的H+浓度为1´10-amol/L，下列说法正确的是 A、a <7时，水的电离受到抑制 B、a <7时，溶液的PH可能为a C、a >7时，此溶液可能是NH4Cl溶液 D、a >7时，此溶液的PH值一定为14-a