Trilobites are index fossils because they a. changed slowly through time c. exhibit specific characteristics b. lived over large areas of the world d. all of the above select the best answer from the choices provided a b c d

Answer: Option D all of the above

Explanation:

Index fossils are the ones which are used to define as well as identify geological periods.Trilobites are one of the earliest known groups of arthropods.There are thousands of species of trilobites that are known and they are found in various parts of the world. The main reasons that trilobites are considered as index fossils because they were found to live in many regions of the world during specific period in the geologic time.They first appeared in the early Cambian period and then increased in number through the Palaeozoic era and finally disappeared at the end of the permian.Trilobites appeared quickly in the geologic time and then moulted just like the other arthropods and thus, are used as index fossils by scientists.

Thus, all the characteristics mentioned in the options are the reasons why trilobites are used as index fossils.

1. true.2. true.3. true.4. false.5. true.the concept of darwin's theory of evolution involves the idea that there are limited resources in a given living environment and that the organisms which live within have variations in their genetic make up due to random mating. the ones with beneficial genetic variations can express certain traits which give them an upper hand in surviving and reproducing in the said environment compared to ones who may have a more disadvantageous variation in traits. over time, the organisms with an upper hand will survive and reproduce more frequently and pass on their beneficial genes while the others die. the result is evolution, where we observe (usually, but not always) eventually, phenotypic distinct changes.