Final answer:
Qin Shi Huangdi did not standardize currency during his reign. Despite his numerous successful standardization efforts, a uniform currency system was not implemented prior to the collapse of his empire.
Step-by-step explanation:
The question asks about which of the following Qin Shi Huangdi, the First Emperor of a unified China, did not standardize during his reign: the widths of cart axles, currency, weights and measurements, or the widths of canals. Qin Shi Huangdi was known for imposing uniform standards on language, law, weights, measurements, and the widths of roads and axles of carts to unify the nation and facilitate administration and trade.
However, it is reported that he was not able to standardize the currency fully before the collapse of his empire. Despite his attempts to unify various aspects of the society and government, currency standardization was not achieved during his rule. His lack of success in standardizing currency stands in contrast to his numerous other standardization efforts, including imposing a unified writing system and making cart axles a uniform width to match the standardized roads.