Final answer:
The statement that Obsidian tools are 500 times sharper than a razor is false, but Obsidian can be finely sharpened. The phrase that best describes Acheulean tools is 'hand-axes made by careful chipping of stones'.
Step-by-step explanation:
The claim that Obsidian tools are about 500 times sharper than a razor is false. While Obsidian can be fractured to produce very sharp edges, saying it is 500 times sharper than modern steel razors is an exaggeration. Obsidian blades are indeed extremely sharp and can produce an edge that reaches microscopic thinness, leading to its use in various surgical tools even today. However, the comparison to modern razors is not quantifiable in the simplistic term as „500 times sharper“. Precision tools like surgical blades are valued for their sharpness, which can be similar to that found in high-quality obsidian edges.
Acheulean tools, described in the provided materials, were hand-axes made by careful chipping of stones (Option a). Acheulean tools represent a significant leap in technology over the earlier Oldowan tools, which were essentially sharpened stones used for cutting, scraping, and chopping. Acheulean hand-axes were far more sophisticated than the Oldowan variety and show evidence of more advanced thought and craftsmanship in their production.