Final answer:
The phrase 'hand-axes made by careful chipping of stones' best describes Acheulean tools, signifying an advancement in prehistoric technology around 1.7 million years ago, with the tools often recognized for their teardrop-shaped hand-axes.
Step-by-step explanation:
Acheulean tools, often recognized for their iconic teardrop shape, represent a significant advancement in the development of prehistoric technological tools by early humans. These tools, dating back to about 1.7 million years ago, were crafted by careful chipping away at stone cores to produce a thinner, sharper, and more sophisticated tool than their Oldowan predecessors. The characteristic hand-axes were not just sharper, but also more efficient for cutting, scraping, and chopping tasks. The term 'Acheulean' comes from Saint-Acheul in France, where these tools were first discovered.
Given this context, the phrase that best describes Acheulean tools would be 'a. hand-axes made by careful chipping of stones'. This phrase captures both the method of production—meticulously chipping away at the stone—and the iconic hand-axe shape that defines Acheulean tools. Far from being simple implements, these tools showcase the early human's growing understanding and mastery of their environment, accomplishing more complex tasks and undoubtedly contributing to their survival and evolution.