Research shows that the four predominant emotions in counseling students are the same core emotions that are typically part of the change process for clients. Specifically, these four emotions are a. Happy, sad, angry, fearful
b. Frustration, dissatisfaction, uncertainty, insecurity
c. Precontemplation, action, maintenance, relapse
d. Depression, anxiety, mania, hypomania

Option A,

Explanation:

As per the conventional study belief’s, there were six main emotions – disgusted, happy, sad, angry, fear and afraid.  

But with the later studies conducted at Glasglow, it became important that there are primarily four major emotions i.e  Happy, Sad, Angry and afraid as it was concluded that anger and disgusted  &  fear and surprise have similar characteristics and they must be removed.  

Hence, option A

"d.) carbon dioxide and hydrogen sulfide"