Task 4In general, the ancient Romans were a practical people. They cared less about philosophy anti pure mathematics than did the Greeks. The Romans were the best of the ancient engineers anti architects. They were brilliant students of Greek geometry and trigonometry, and they applied their knowledge to the constructions of fine bridges, roads, aqueducts, and public buildings.They knew about the smelting of iron ore, but they used the iron they produced mainly for spears, swords, and shields, rather than for building construction.While the Romans accomplished practical wonders, they did very little theoretical scientific thinking. Because of their frequent wars, many of their inventions were no more than improvements in the design of Greek weapons with which they were familiar.There are two reasons for the Romans neglect of philosophy and pure mathematics. First, they were apparently too busy conquering nearby nations and forming them into a rapidly growing empire to waste much time on abstract thinking. Secondly, they were handicapped by the rigidity of their numerical system. The Romans did all of their arithmetic on an abacus, the ancient counterpart of the modem computing machine. Their number system discouraged the study of pure mathematics. Which is mentioned as the reason for which many Roman inventions were based on Greek weapons（）

A. They learned Greek geometry and trigonometry.
B. They made Greek spears, swords, and shields.
C. They were involved in frequent wars.
D. They employed Greek engineers.