Final answer:
The correct description for Acheulean tools is 'hand-axes made by careful chipping of stones,' reflecting early human craftsmanship in stone tool-making.
Step-by-step explanation:
The phrase that best describes Acheulean tools is 'a. hand-axes made by careful chipping of stones'. These Acheulean hand-axes are characterized by their distinctive teardrop shapes, crafted using a technique known as 'knapping,' where a stone core was struck with another stone to create a sharp edge.
The creation of Acheulean tools marks a significant advancement in early human technology, dating back to roughly 1.6 million years ago, and was predominantly used by Homo erectus. These tools exhibit a great deal of skill and craftsmanship, evidencing early humans' developing cognitive capacity for planning and tool-making.