The one that demonstrates leadership quality, strategic intelligence, how to use analytical skills etc and ensure their team survives and can complete the mission. In otherwords they'd be able to lead a team hence Shikamaru became a Chunin. Sarada and Shikidai would fit the bill based on how they did things in the chunin exam.
So Shikimaru was the ONLY one promoted to Chunnin that time? How many exams are needed in order for everyone to become Chunnin?
The one that demonstrates leadership quality, strategic intelligence, how to use analytical skills etc and ensure their team survives and can complete the mission. In otherwords they'd be able to lead a team hence Shikamaru became a Chunin. Sarada and Shikidai would fit the bill based on how they did things in the chunin exam.
Sarada lost her chunin rank when she ran like an idiot against shinki.