44. Using a Doppler ultrasound device, fetal heartbeats can be detected by the twelfth week of pregnancy.
A. Using a Doppler ultrasound device, fetal heart-beats can be detected by the twelfth week of pregnancy.
B. Fetal heartbeats can be detected by the twelfth week of pregnancy, using a Doppler ultrasound device.
C. Detecting fetal heartbeats by the twelfth week of pregnancy, a physician can use a Doppler ultrasound device.
D. By the twelfth week of pregnancy, fetal heartbeats can be detected using a Doppler ultrasound device by a physician.
E. Using a Doppler ultrasound device, a physician can detect fetal heartbeats by the twelfth week of pregnancy.
 
1. 修饰：逻辑主语和主句主语不一致 （一级排除A,B ）
, it modifies heartbeats, the nearest free noun in the main clause; that is, choice A says that the heartbeats are using the Doppler ultrasound device
 前置和后置状语的逻辑主语和主句的主语一致，考察是否合理
 
2. 句子中心：（二级排除C ）
改变分词成主句，造成句子中心改变，而且扰乱了逻辑关系。 前置状语的动作通常发生在主句之前。
the wording in choice C suggests that physicians can use a Doppler ultrasound device after they detect fetal heartbeats
 
D为什么不对？？？？
choice D the phrase using ... device should follow physician, the noun it modifies
 
By the twelfth week of pregnancy, fetal heartbeats can be detected using a Doppler ultrasound device by a physician
By the twelfth week of pregnancy, fetal heartbeats can be detected by a physician using a Doppler ultrasound device