A.3 B.1/3 C.9 D.1/9
A.蓄電池; B.發(fā)電機; C.有蓄電池和發(fā)電機兩種; D.干電池
A.是升壓變壓器; B.是降壓變壓器; C.初級次級的電流比為1:100; D.初級次級的電壓比為100:1