The correct statement is 1: "Viruses lack enzymes necessary for the generation of energy." This is accurate because viruses do not possess the cellular machinery required for metabolism or energy production; they rely entirely on host cells to replicate and generate metabolic energy. Statements 2 and 3 are incorrect as viruses cannot be cultured in any synthetic medium—specific host cells are required for their propagation—and they can be transmitted by both biological vectors (like mosquitoes) and non-biological means (such as direct contact or airborne routes), making them versatile in their transmission methods. This understanding of viral biology is essential for grasping the complexities of infectious diseases, which is a relevant topic in the UPSC syllabus.