The correct answer is - A. Embracing Taoist philosophy.
The first Chinese Emperor, Qin Shi Huangdi, was a great leader and is very respected in China even nowadays for his multiple achievement, and they are indeed in abundance, but the embracing of the Taoist philosophy is not one them.
Qin Shi Huangdi is well known for making the initial version of the Great Wall so that China is protected from the Mongols and Turkic people from the north, making a standardized written language, laws, implementing standardized measurements, making one of the most amazing antique piece of architecture, the Mausoleum with the terra-cotta Army, but most importantly, his biggest achievement was that he unified the Chinese people and created one strong, big, country, to which he set up the basis for future development and progress.