To Prevent an Adverse Reaction,it Is Essential to Monitor Which

To prevent an adverse reaction,it is essential to monitor which of the following when administering carbogen to a patient?
1) Heart rate
2) Blood pressure
3) Respirations
4) The patient's mental status

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