Superconducting materials are used in which of the following application?
1. Magnetic Resonance Imaging (MRI).
2. Magnetic Resonance Spectroscopy (MRS).
3. High-speed switching and signal transmission for computers.
4. High-speed magnetically levitated trains.
Select the correct answer using the options given below:

A. 1 and 2 only

B. 3 and 4 only

C. 2, 3 and 4 only

D. 1, 2, 3 and 4

Answer: Option D