Why would flatboats not work on all means of river transportation

The first task here is to trace furrows, ripping up the maze of paths, and then excavate a deep trench in the ground. the second comprises refilling the trench with other material to make a foundation for the road build-up. the ground must not give way nor must bedrock or base be at all unreliable when the paving stones are trodden. next the road metalling is held in place on both sides by kerbing and numerous wedges. how numerous the squads working together! some are cutting down woodland and clearing the higher ground, others are using tools to smooth outcrops of rock and plane great beams." - a poem by statius praising the via domitiana, written 1st century c.e. using the prompt, another way that road building led to expansion besides trade was that it a) led to a uniform law system. b) created less class divisions due to economic expansion. c) allowed for the creation of unique architectural styles. d) allowed the military to move people and supplies further.