How did the Qin dynasty come to power?

In 221 BC, the Qin dynasty rose to power because they were one of the Warring States' most powerful dynasties. ... When all of the warring states were finally conquered, the only one left was the Chu dynasty. The Qin went to war with the Chu, and they defeated the Chu at last.

The Qin dynasty rise to power in 221 BC because they were one of the most powerful dynasties in the warring states. When this dynasty was starting to expand themselves they allied with the Zhou dynasty. When they finally had conquered all the warring states, the only one left was the Chu dynasty. The Qin went to war with the Chu and they finally defeated the Chu.

i believe it is the second one.   if correct plz mark brainliest.