Which ratios are useful in determining the age of rocks or sediments?

The correct choice, which includes uranium-helium and uranium-lead ratios, is essential for determining the ages of rocks and sediment due to the properties of the isotopes involved. Uranium-lead dating is one of the oldest and most reliable methods of radiometric dating, particularly useful for dating zircon crystals in igneous rocks, with a half-life of about 4.5 billion years. This method involves measuring the ratios of uranium isotopes, which decay into lead isotopes over time, allowing for the calculation of the time that has elapsed since the mineral crystallized.

Uranium-helium dating, on the other hand, is a method that capitalizes on the decay of uranium to helium, which allows for dating of more recent events and enhances the precision of understanding geological and thermal histories. This dual approach provides a complementary perspective in age dating by covering a range of geological timescales.

Other combinations of isotopic ratios mentioned do not serve as effectively for the purpose of dating rocks and sediments when compared to uranium-based isotopes. While they may have applications in specific contexts, uranium-helium and uranium-lead are notably more accurate and widely utilized methods in geology for obtaining age estimates.