910.    Using a Doppler ultrasound device, fetal heartbeats can be detected by the twelfth week of pregnancy.
(A) Using a Doppler ultrasound device, fetal heartbeats 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 heart-beats 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.

答案选E，没有问题，OG11对B的解释是 the modifying phrase has no referent。而A 的解释是phrase 错误德修饰了 fetal heartbeats。
为什么对B的解释是没有修饰对象啊，意思是只能把using 放在前面吗？ 其它的过去分词修饰或分词修饰也是这样吗？

我来简单回答一下，参考。选e没有问题
b中的  ，useing结构是有歧义的，可以理解为主句Fetal heartbeats can be detected ...的方式壮语从句，同时也可以理解为修饰前面的 twelfth week of pregnancy，这是问题1。
然后你就按照这样l理解看看，不管是上述那种情况带进句子用useing都是不对的，做状语 Fetal heartbeats  useing，f病 发出 use这一动作？还是twelfth week of pregnancy 发出useing这一动作？
这就造成了没有指代修饰的问题