When a machine is given an input line of words as below, it rearranges them following a particular rule in each step. Given below is an illustration of input and rearrangement at each step:

Input: horlicks horizon hopefully hookworm hornbill hormone hopscotch hoover

Step I: hornbill horlicks horizon hopefully hookworm hormone hopscotch hoover

Step II: hornbill hormone horlicks horizon hopefully hookworm hopscotch hoover

Step III: hornbill hormone horlicks horizon hopscotch hopefully hookworm hoover

Step IV: hornbill hormone horlicks horizon hopscotch hopefully hoover hookworm

Step IV is the last step of rearrangement and final output. Now, based on this pattern, answer the question relating following input:

Input: letterhead leucocyte leprous letdown lettuce leopard leverage lessen

Which of the options will be the 4th step?

The logic that is followed in the given steps in this input output is given as follows:

1) Word are arranged in Descending order according to the English dictionary order i.e. in reverse dictionary order from the left end.

2) In each step only one word is shifted.

This process is repeated till we obtained the final output in step IV.

Based on this logic we obtain the steps of the given input as follows:

Input: letterhead leucocyte leprous letdown lettuce leopard leverage lessen

Step I: leverage letterhead leucocyte leprous letdown lettuce leopard lessen

Step II: leverage leucocyte letterhead leprous letdown lettuce leopard lessen

Step III: leverage leucocyte lettuce letterhead leprous letdown leopard lessen

Step IV: leverage leucocyte lettuce letterhead letdown leprous leopard lessen 

Step V: leverage leucocyte lettuce letterhead letdown leprous lessen leopard 

Hence, "Option 4" is the correct answer.