Archaeology is a science that studies how to find and acquire the physical relics of ancient human society, and how to study the history of human society based on these relics. In other words, archaeology is a science subject based on the discovery of science and the study of history through objects. According to the above definition, which of the following is archaeology? ['Author of ancient books.', 'Identification of the authenticity of ancient paintings at auction.', 'Estimating the value of the exhibits.', 'Research on the age of agricultural tools unearthed.']