The sentence that describe both techniques historians use when synthesizing evidence is A. Comparing and contrasting historical sources.
The historian usually carry out synthesizing of evidence through the process of making comparison between the historical sources.
It should be noted that before they can conclude about the authenticity of a particular information, the historian will go through the information that they just discovered and contrast with the sources that are available and this will help them to come out with the fact about the information.
Therefore, option A is correct.
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