og-44

jzchina

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.

關於這道題的答案c，og的解釋是choice c suggests that physicians can use a doppler ultrasound device after they detect fetal heartbeats.選項c“Detecting fetal heartbeats by the twelfth week of pregnancy, a physician can use a Doppler ultrasound device.”是邏輯主語結構，前面的部分和主句之間有先後關係嗎？我不知道有這種説法，請指點！