How to add Actual request body in pre-request script without using environment variable

Help Hub
4

Based on the Environment variable(conditionally) Option A, B or C, I have to take a different request. How to achieve that?

option A:

{
    "profile": {
        "firstname": "firstname",
        "lastname": "lastname",
	    **"mobile" : "{{mobile}}"**
    }
}

option c:

{
    "profile": {
        "firstname": "firstname",
        "lastname": "lastname",
        **"email": "{{email}}",**
       **"mobile" : "{{mobile}}"**
    }
}

Option B:

{
    "profile": {
        "firstname": "firstname",
        "lastname": "lastname",
        **"email": "{{email}}"**
    }
}

Note: Just the request body is dynamic based on Environment variable. Hader/URL and method remains the same.

Appreciated your help