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.

Let me give you an example: Rope and its Usage
The answer to this example can be: Rope
Here is why: The word 'Rope' is the key subject here, while Usage is a property of Rope.

OK. solve this:
Three hawser-laid ropes each of 120 fathoms, laid up together in the opposite direction to that of their own lay, will form a cable-laid rope, 100 fathoms in length.
Answer:
Three hawser-laid ropes