Oldest fossils usually: .1. are found in the deepest strata 2. have the longest half-lives 3. are found in sediments formed during the Cenozoic era 4. contain more radioactive isotopes than younger fossils 5. are found above younger fossils

Option (1)

Explanation:

The above given question based on the law of superposition. This law describes that the rocks that are found at the basal portion of an undisturbed sedimentary sequence are considered to be the oldest rocks as the sediments deposited during that time gave rise to the formation of that bottom layer, and with successive deposition within the same place, forming the top layer is considered as the youngest rocks.

So, from this context, it can also be concluded that the fossils that were deposited in that bottom rocks are the oldest fossils, whereas, those that are deposited at the apex rock layer are the youngest fossils.

Thus, the oldest fossils are found in the deepest strata.

Therefore, the correct answer is option (1).