Answer:
D. They invented the numeral zero and the decimal system of numbers.
Step-by-step explanation:
Before Gupta empire introduced this numerical systems, the people who live in their territory used comparisons with another object as a unit of measurement.
Example: 3 bag of rice, one arms of cloth, etc.
This make tradings and architecture becomes really complicated since it is easier for people to cheat one another with such vague unite of measurements.
The introduction of numeral zero and the decimal system accelerate the development of mathematics in this area dramatically, they called it the Gupta Numerals.
The numerals make it possible for the people to be more productive, for example, they use it to help them make proper adjustment and measurements to build tools and buildings. Over-time, the numeral system keep undergoing change and development, until it eventually developed into what we see today and used in higher-level of mathematics.