Which of the Following Are True About NO₂

Which of the following are true about NO₂?
1) NO₂ levels greater than 10 ppm can cause hemorrhage, pulmonary edema, and death.
2) NO₂ is produced spontaneously whenever NO is exposed to O₂.
3) The Occupational Safety and Health Administration (OSHA) safety limit for NO₂ exposure is 5 ppm.
4) NO₂ exposure should be kept below 5 ppm during NO administration.

A) 1 and 3 only
B) 1, 2, and 3 only
C) 3 and 4 only
D) 2, 3, and 4 only