题目

Beijing retiree Yang Hua was devoting a lot of his time to staying fit by completing his favorite exercises. But, according to his doctors, his routine may have done more harm than good—he recently suffered an illness because he was exercising the wrong way. “Many people today still do not know how to exercise in scientific ways. As a result, they do not gain from the exercises and in fact may even hurt themselves, said Yang Zeyi, an executive board member of the Asian Council of Exercise and Sports Science. Health experts said that a cardiopulmonary（心肺的） exercise test is necessa1、下列叙述中，正确的是（　　）A、含有一个未知数的等式叫一元一次方程B、未知数的次数是1的方程是一元一次方程C、含有一个未知数，且未知数的次数是1，系数不等于0的整式方程叫一元一次方程D、含有一个未知数，次数是1的代数式叫一元一次方程