When an object falls freely under gravity most distance is covered in which second of it`s journey in first second second second or third second?

Dear student,

Consider the following equation of motion-



For all three given intervals of time, time is 1 second and a=acceleration due to gravity.
Hence the period which has higher initial velocity will travel farther in that second.

Since the body continuously accelerates over time, the speed keeps on increasing and in the given case, the body will have highest intial velocity in the third second.