楼梯是多层建筑的非重要垂直交通设施。
参考答案:错
He insisted ________ me with the handbag, though I told him I could manage it myself. [ ]
A. help
B. in helping
C. on helping
D. to help
乙炔装置电除尘器共有()台,其供电电源采用的是()型高压直流电源。