问题
选择题
下列说法正确的是 [ ]
A．两点之间的直线最短
B．当时钟指向3：30时，时针与分针的夹角是90°
C．平面内，过一点有且只有一条直线与已知直线垂直
D．平面内，过一点有且只有一条直线与已知直线平行
答案
答案：C
搜题请搜索小程序“爱下问搜题”
下列说法正确的是 [ ]
A．两点之间的直线最短
B．当时钟指向3：30时，时针与分针的夹角是90°
C．平面内，过一点有且只有一条直线与已知直线垂直
D．平面内，过一点有且只有一条直线与已知直线平行
答案：C
阅读下面短文，掌握其大意，然后从1～15各题所给的A、B、C和D项中，选出最佳选项，并在答题卡上将该项涂黑。 Some passengers won’t turn off their mobile phones or iPads during takeoff or landing. It happens on almost every now. It’s time to turn off personal electronic devices when the plane’s door . However, there’s always at least one person who keeps talking, texting, playing, watching or emailing — and strict orders to power down during flights. “People have become so to those devices, and a lot of people whether they really need to turn them off,” says an airhostess from Southwest Airlines. Is turning off the devices really in the first place? Lots of passengers have doubted about the of leaving devices on. They think one cell or message or game isn’t going to down the plane. Indeed, there’s no scientific evidence that having devices powered on during takeoff and landing would cause a , only that there is the potential of a problem. In the US, pilots are allowed to use certain electronic devices during takeoff and landing, but if passengers’ devices are tested at the same time, it may lead to wrong warnings and readings on the aircraft instruments. In some studies researchers found mobile phones could global-positioning satellite systems or other aircraft systems. Though the effects are slight, they could result in disaster. If even the possibility of disaster exists, it’s better to turn them off during takeoff and landing.
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