What structure is found in all cells that encloses the cell to form the outside?

That's called the cell membrane. It encloses both prokaryotic, eukaryotic, plant and animal cells.

In the case of eukaryotic cells, it is the outermost layer, in the case of prokaryotic cells, it is not.

Hope it helped,

BioTeacher101

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.