part a:

i knew this moment would come, but i thought it would be when m was a little older for some reason.
a few weeks ago m and i were sitting on the couch hanging out, and she was staring at my ears intently. finally she said, "mommy, why no put on ears? roro put on ears." matt and i knew that at some point she would ask why she wears implants and not everyone else does. after all, she has a set of toy cochlear implants that came with a stuffed animal when she got her implants, and she often plays with them by trying to put them on me. they look identical in scale and color to hers, so they look like the real thing. she notices when people have hearing aids. she'll point behind our ears sometimes, but when she actually asked me why she had them and i didn't, it took me off guard.
i've used the word deaf with her, and explained that she is deaf, and that's why when her ears are off she doesn't hear, but i don't think she totally understands it yet. i think she assumes we all stop heraing once we take baths or showers, or when we take naps or go to bed. i think she thinks it is normal to attach a device to one's head with wig tape, and to lose sound every so often when the implants coil falls off.
so i began a conversation that will last a very long time-throughout our lives i imagine, about what it means to be deaf, and to have implants, why she has them and we don't. it was short, and i tried to use words she would understand. for now i said her implants were special ears that helped her listen and speak, and that when she was born her ears couldn't hear, but when mommy and daddy were born our ears could hear, so we didn't have special ears. moments later she moved on to playing, and that was it.
then the other day i was changing ruby's diaper. m was laying on the bed next to her, snuggling up to her sister as she likes to do. m pointed at her head and said, "mommy, ruby no have special ears. roro, special ears."
so i guess she remembered at least a snippet of what i said.
part b:

this is how you know you have a deaf child with implants-
multiple times when i have been holding ruby i check her head to make sure her implant coils haven't fallen off. then i remember-oh wait. she doesn't have implants.
it's funny what becomes normal. every time ruby startles to a sound it startles
me. i often forget that she can hear at this age. it became so normal to us that m couldn't hear (even with her hearing aids) until she had her implants that whenever ruby responds to sound it kind of surprises me.