I'm sure Altair is the answer Colleen was looking for but it wasn't actually the first. MITS Altair got a big writeup in Popular Electronics which got a lot of people interested in it but a few other machines predated it (I used to have that issue but not knowing how pivotal that article would be I probably threw it out).
I've only heard of one of them, so I'll go for that one.
Hope I got It right "Heart Pounding"
It's the Altair 8800 I'm sure o_O
So A :D
The answer is A) Altair
I think D