How do people transport/move ideas in greece?

Transport in Greece have undergone significant changes in the past two decades, vastly modernizing the country's infrastructure. Although ferry transport between islands remains the prominent method of transport between the nation's islands, improvements to the road infrastructure, rail, urban transport, and airports have all led to a vast improvement in transportation. These upgrades have played a key role in supporting Greece's economy, which in the past decade has come to rely heavily on the construction industry.

When trading they can express ideas as well.

The correct answer is C.

When you're solving a system of equations, the solution is equal to the coordinate of the intersection. A coordinate always includes both an x and y value.