When your eyes feel tired from looking at close objects, it to look at distant objects for a few minutes. why do you think this ?

When we look at close object, it utilizes energy for muscle contraction and some relation due to which eyes feel tired (muscle contraction helps the aye to focus various objects according to the distance). After that when we look at distant objects they seem to be clear because in doing so our muscles get relaxed that's why the objects at distant appears clear for a while.

the trilobite is used as an index fossil for various geologic time periods as specific types of the trilobites were present in different geological time periods. they are a group of marine arthropods belonging to the class of trilobita.

explanation:

option c is the correct answer.