Final answer:
The boundary between Earth's atmosphere and outer space is widely recognized at the Kármán line, which is located about 100 kilometers or 62 miles above sea level, closest to option B. About 60 miles up.
Step-by-step explanation:
When discussing entering outer space from Earth's atmosphere, there is not a universally agreed-upon altitude as the boundary, but a commonly accepted standard is the Kármán line, which is about 100 kilometers (62 miles) above sea level. This line is approximately at the edge of the thermosphere and before the exosphere, where the atmosphere becomes so thin that it's practically non-existent. Therefore, the correct answer to the question 'At what point do you leave Earth's atmosphere and enter outer space?' is B. About 60 miles up, which is close to the Kármán line at 62 miles or 100 kilometers up.