Given the task definition, example input & output, solve the new input case.
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: Rope and its Usage
Output: Rope
The word 'Rope' is the key subject here, while Usage is a property of Rope.

New input case for you: Construction and characteristics of wire rope.
Output:
wire rope