题目

Bicycle Safety Operation  Always ride your bike in a safe, controlled manner on campus(校园). Obey rules and regulations. Watch out for walkers and other bicyclists, and always use your lights in dark conditions. Theft Prevention  Always securely lock your bicycle to a bicycle rack---even if you are only away for a minute. Register your bike with the University Department of Public Safety. It’s fast, easy, and free. Registration permanently records your serial number, which is useful in the possible recovery of the bike stolen. Equipment Brakes  Make sure that they are in good wo17．在△ABC中，三边a，b，c满足a2=b2+c2+bc，则角A等于（　　）A．30°B．60°C．120°D．150°