Final answer:
Scientists have determined that Earth is at least 4.3 billion years old using uranium-lead dating. This method calculates the age of a mineral by measuring the ratio of uranium-238 to lead-206 and utilizing the known half-life of uranium-238. Earth's oldest minerals have been dated to around 4.4 billion years old using this technique.
Step-by-step explanation:
The determination that Earth is at least 4.3 billion years old has been made possible through a technique known as uranium-lead dating. This method is based on the radioactive decay of uranium-238 into lead-206. Uranium-238 has a long half-life of approximately 4.5 billion years, which makes it suitable for dating very old rocks and minerals. Scientists can measure the ratio of uranium-238 to lead-206 in a sample, and because we know the half-life of uranium-238, we can calculate the age of the rock. This is confirmed by the oldest known minerals on Earth, such as zircon crystals, which have been dated using uranium-lead dating to be around 4.4 billion years old.
It is important to note that other methods such as potassium-argon dating and rubidium-strontium dating also exist and are used for similarly aged materials. However, uranium-lead dating is particularly useful for determining the age of the Earth's crust and is a key tool in geological dating.
The correct answer to the question "Which allowed scientists to determine that Earth was at least 4.3 billion years old?" is B. Uranium-lead dating.