What I know is that I definitely, under no circumstances want to go with A. Jing never struck me as a guy that is willing to bend his own personal principles for something the voters perceive as a greater good. This whole situation reeks of UNIFIED TIBET hysteria that could have very well placed zhang manxing on Tufan throne. In the end, we found a way to resolve it in a much better way, even though we could not have guaranteed that such a resolution will be available when we made the choice.
It is about B or C for me, but I really don't want to sacrifice a 'quite possibly guilty person' to save an innocent person. If your goal is also to make you feel better about the choice, this is not the way to advertise it.
Since we didn't procure any evidence on our own, extracting it from Fu Xia at this point does not attract me in the slightest. I think I'll go with B for this one. Whether it will save Zheng's life on not is up in the air, but I am positive it won't result in the same thing as A. Xiaofang was atttacked with the same poison after Zheng was apprehended, so if the angle of the prosecution is that he could have secretly known a needle technique, we are likely to put Zheng's involvement in doubt.
I believe this would rock the boat quite hard, but I do not really care about it.
Edit: In any case, as cynical as it may sound, our goal is not to save Zheng or to find out who killed Du Yao. Our goal is to find the manual.
Since the culprit left an obvious trace to Du Yao and made an effort to place blame on chief Zheng for the murder, I am guessing that vindicating the chief of guilt would throw a wrench in their plans. We should have learned by now that playing someone else's game by their rules never ends well (Bai Jiutian, anyone?), and A has the culprit achieving pretty much everything they wanted and beheading the pursuers to boot.
Now, I guess the current set of choices means that we messed up. But where and when did we possibly go wrong? We gathered what we could from the corpse, the crime scene and the daughter. We also got something out of search for Xiaofang, so it's not like we failed there.
We only gained a vague, potentially false confirmation of Jinkong Sect's involvement from the servants through Fu Xia.
We did not procure anything from Du Yao's underlings.
We did not let Fu Xia check on Jinkong Sect.
We did not enlist Yunzi's help.
We did not detain Fu Xia.
So far, most of these points that may have or may have not contributed to our failure have to do with either Fu Xia, Jinkong Sect, or both. There are ample reasons to check both of them, but it would be pretty shity if we get the wrong guy. And I have a really hard time trying to connect Fu Xia and the Xueguizi technique that killed Du Yao and injured Xiaofang.