Final answer:
Sydney Carton saves Charles Darnay during his trial in England by using their physical resemblance to create doubt in the minds of the jury and cast uncertainty on Darnay's guilt.
Step-by-step explanation:
In Charles Dickens' novel A Tale of Two Cities, Sydney Carton saves Charles Darnay during his trial in England by taking advantage of their physical resemblance. Carton had been present in the courtroom during the trial and realized that the witnesses were identifying Darnay based on his appearance.
With Darnay's defense attorney questioning the reliability of eyewitness testimony, Carton uses his striking resemblance to Darnay to create doubt in the minds of the jury and cast uncertainty on Darnay's guilt. This strategy ultimately leads to Darnay's acquittal.