Which of the following statements are true?a. R-12 is not used due to ozone depletion problemb. R-13 is not preferred for blood storage at as low as -90°Cc. R-21 is suitable for automobile air-conditioning.d. R-22 is the most widely used refrigerant for large central air-conditioning installations.

• A. Only a and b are true
• B. Only a, c and d are true
• C. All a, b, c and d are true
• D. Only b, c and d are true