The wheel has been used by humans since nearly the beginning of civilization and is considered one of the most important mechanical inventions of all time. Most primitive technologies since the invention of the wheel have been based on its principles, and since the industrial revolution, the wheel has been a basic element of nearly every machine constructed by humankind. No one knows the exact time and place of the invention of the wheel, but its beginnings can be seen across many ancient civilizations. According to this passage, the wheel is an important invention because:
a. it is one of the world’s oldest inventions
b. it forms the basis of so many later inventions
c. it is an invention that can be traced to many cultures
d. it is one the world’s most famous inventions
