You will be given a definition of a task first, then some input of the task.
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.

When made of manila or sisal, the fibres of the rope are treated with a rot-proofing solution during the first stage of rope-making, when the fibres are being combed into ribbons.
Output:
the fibres of the rope