Sentences of a paragraph are given below in jumbled order. Arrange the sentences in the correct order to form a meaningful and coherent paragraph.

A. Archaeologists are guys who have been meticulously excavating.
B. These people go through thick layers of dirt to investigate human artefacts, particularly those from the prehistoric era.
C. They have discovered old city ruins, strewn tools, and writing and pottery shards.
D. In an effort to find the solutions to numerous problems, they have attempted to put all these hints together like a huge jigsaw puzzle.