The basic structures of all living organisms are cells. Cells are the structural and functional units of life. They are responsible for carrying out various biological processes and are the building blocks of all living organisms. To get this answer, you could have eliminated choices A and C because atoms and quarks are not specific to living organisms and are instead fundamental particles that make up matter. Organelles, on the other hand, are specialized structures within cells that carry out specific functions, but not all living organisms have organelles. Therefore, the correct answer is choice D, cells.
