How to remember dates and events in history

Which of the following matches an event in the history of life with the correct geological era ?

In which group of molluscs torsion is a ery important event in the life history?

Question Stimulus :- Out of the given options, choose the one which is the correct passive voice of the sentence given below. Did he remember the date and time ?

How Important Are Dates

26th October, 1947 is an important date in the Indian history, because of

Mayank remembers that the examination is after 18^(th) December but before 21^(st) December, while Suraj remembers that the examination is before 24^(th) December but after 19^(th) December. On which date of December is the examination?