Could very well be. Not sure of middle one.

Could B and C possibly be the same variety? They look quite similar, at least to my inexperienced eye.

Here's a pic of B from a different angle. It's leaves are much narrower and shorter than C's and I think both plants are full sized so B is smaller overall than C is.

C has some dark green vertical striping along the edges of the leaves that B doesn't have. So, I don't think they are both Robustas, but they do look similar, don't they.

I beleive 'B' is a yound S. trifasciata and 'C' is S. t. Robusta. Note as stated the wider leaves of Robusta.
the standard trifasciata can get large. Some reaching 60 inches. Mostly average is 36 inches.
Stush

That's what I thought when I bought it...that it was a baby and would grow into a full size standard sans...but it's not really getting any bigger and doesn't seem to be growing at all. It's just kind of ...there. :) I guess I'll have to wait and see what happens.

Here's a pic of plant A...is it Black Gold or Black Star?? Anyone? :)

That's a good question, and here is the answer....
'In primis' there is no mention of the cv. name 'Black Star' anywhere. Then, You will soon realize that in Chahinian's mind (The S.trifasciata Var. p.42) 'Black Gold' is a totally different plant. But I know very well this plant: it is grown by the millions in Holland and it is swiftly wiping away all the others in the 'Futura' group. In the trade it is named 'Black Gold' and it is a cv. of 'Futura Superba' (or 'Futura Simplex' as for Chahinian) with no cross stripes. From leaf cutting , it produces all green, no striped, plants like 'Onyx' (sensu Grootscholten) or a reversión without yellow margins that often sprouts from Ziad's 'Midnight Shine'. (another controversial cv, indeed!). And we have a 'Laurentii' size of this cv., often named 'Black Gold' , too! My plant, by the way, doesn't reach the size of a full developed 'Laurentii', but stays at about 50cm of heigth. Leaves are half the width of any 'Futura', and half the heigth of 'Laurentii'. This cv. may well be Chahinian's 'Compacta' (pag.23). On my experience it only produces all green , not banded plants from leaf cuttings. These plantlets, are, of course, 'Nelsonii'. Need I say more? confused? well, me too!

Roberto,
Always love your replies (reports). Seems right on.
I have just heard of 'Black Star' refering to a S.t. hahnii simular to Hahnii Marginated. Seems to have white edges instead of yellow. Also can't be sure of nursery names now.
Jen,
Don't expect the first crown (mother plant) to get much bigger. They increase in size with each new pup produced. In fact, if the mother is removed and repoted up, it will stay smaller while it's new pups will continue to increase in size. Some beleive that is how they came up with the hahnii group but I don't buy that.
Stush

Thanks for all the replies!

So, it looks like A is a Black Gold. B is stil a mystery. And C is a Robusta? Here's another pic of C.

Do I see wide, solid green margins on the edges of that central leaf? Or is that just a trick of the lighting? ;-)

I saw that too Beth, You can't judge a plant by one leaf. If all the leaves had that marking, it would look like 'Eve'. Opposite of 'Whitney'. Notice I said looked like.
Stush

Still, I wonder what would happen if she took that one interesting rosette out of the pot and planted it by itself... would it make more green-margined plants? Could be a fun experiment to try!

Yep, those are wide green margins on some of the leaves. Maybe one day when it needs to be repotted I'll try separating that one rosette and planting it by itself and see what happens. But for now, I just had to replace all the soil due to fungus gnats so I just want to leave the plant how it is for now.
I had assumed that the central rosette with the margins was the mamma and the other two rosettes were pups, but who knows how they got started since I bought the plant at a supermarket. Hmmmm..... :)