When I inject my dose into my thigh, should my leg be:

A) Completely relaxed, sitting on the side of the bed, for example, legs dangling, foot not on the floor.

B) Not flexed, but also not entirely relaxed, on a chair, feet flat on floor.

C) Completely flexed, tension in the muscle.

D) Standing

I usually do option A. Legs dangling, completely relaxed. Option B, it seems, would also be alright, I assume. But the other day, a friend of mine mentioned that he takes his dose while standing, with obvious tension in the muscle. Now, I would assume you wouldn't want to choose option C. It seems like injecting into a completely flexed muscle would not only be more painful, but also have a bit more resistance to the dose going in (if that's even a thing..?) Any insight would be appreciated. Thanks.

Also, does it have to be in the thigh? I assume I could also dose into any, larger, muscle. In my butt cheek, for example?

Thanks again.