The correct option is
A Work of thousands of people
The correct answer is Option B - Work of thousands of people.
The question is on what is needed to complete a small task or thing.
The first sentence of this passage, "People are ... depends upon the work of several thousands of persons", clearly mentions that comfortable living depends on the work of several thousands of people.
The remaining passage is an elaboration of the first statement. It goes on to explain how a morning cup of tea is the work of thousands of people, "This cup of tea... thousands of people."
The other options A,C and D are an explanation of the main point stated by the writer. He explains how several types of works, various machinery and connected works involve the work of thousands of people in one small task.
This conclusion is made from various sentences in the passage like, "Consider further ... required for sugar mills." and "The production of this ... workers are employed." .
Therefore the main requirement for a small task to be completed is 'the work of thousands of people'.
Hence Option B is the correct answer.