他励直流发电机的外特性，是指发电机接上负载后，在保持励磁电流不变的情况下，负载端电压随负载电流变化的规律。
1、正确Iam____gratefulforthemanykindnessesyouhaveshownmyson.
Onnoaccount____everleavethebabyathomealone.
I’veneverbeenoutofChina___________.Whataboutyou?
TheBentPyramidoutsideCairo__________ancientEgypt’sfirstattempttobuildasmooth-sidedpyramid.
____Thewaterleftinthekettle,thedoctorputseveralthingsheunwrappedfromahandkerchief.
