Explanation:

The Nobel Prize in Physics 2021 was awarded for groundbreaking contributions to our understanding of complex physical systems. One half was awarded jointly to Syukuro Manabe and Klaus Hasselmann for the physical modelling of Earth's climate, quantifying variability and reliably predicting global warming. The other half was awarded to Giorgio Parisi for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales. Therefore, all three scientists—Syukuro Manabe (a), Klaus Hasselmann (b), and Giorgio Parisi (c)—were recipients of the Nobel Prize in Physics in 2021, making option (4) the correct choice. Options (1), (2), and (3) are incorrect as they exclude one or two of the actual winners.