Statement 1 is correct: Viruses that infect bacteria are known as bacteriophages or phages. These viruses use bacterial cells as hosts to replicate and propagate. Statement 2 is correct: Certain viruses, called mycoviruses, can infect and replicate within fungal cells, using them as hosts. Statement 3 is correct: Viruses that infect plants are known as plant viruses. They can hijack the cellular machinery of plant cells to replicate and spread within the plant. Hence, option D is the correct answer.