In this task, you are given a sentence. You must find the primary subject in the supplied sentence. The output must be a sub-sequence in the sentence.

Example Input: It is impervious to saIt water, and so it is very suitable for slings, falls, berthing hawsers and tow- ropes.
Example Output: It

Example Input: This process is known as 'spinning', and the yarns are said to be spun left- or right-handed, according to the direction of twist.
Example Output: This process

Example Input: It should therefore be examined frequently for signs of deterioration.
Example Output:
It