With reference to carbon nanotubes, consider the following statements: 1. They can be used as carriers of drugs and antigens in the human body. 2. They can be made into artificial blood capillaries for an injured part of human body. 3. They can be used in biochemical sensors. 4. Carbon nanotubes are biodegradable. Which of the statements given above are correct?

1. Statement 1 is correct. Due to their high surface area-to-volume ratio and ability to be functionalized, carbon nanotubes (CNTs) have been extensively researched as potential carriers for targeted delivery of drugs and antigens within the human body. 2. Statement 2 is incorrect. While the concept of using nanomaterials for tissue engineering, including potentially creating structures mimicking blood capillaries, is explored, making functional artificial blood capillaries from CNTs for practical use in an injured part of the human body was not an established application as of 2020. 3. Statement 3 is correct. CNTs exhibit unique electrical properties that are sensitive to their surrounding chemical environment. This sensitivity allows them to be used effectively in biochemical sensors for detecting various molecules and biological agents. 4. Statement 4 is correct. Studies have shown that certain types of carbon nanotubes can be degraded by enzymatic processes within biological systems (e.g., by peroxidases present in neutrophils), indicating that they possess biodegradable properties, although the degradation process can be slow and depends on the specific CNT characteristics. 5. Therefore, statements 1, 3, and 4 are correct.