It would be B.
B is the nucleus, which contains all the DNA inside of it.
A: I'm pretty sure this is the Mitochondrion, which "is the powerhouse of the cell," as has probably been drilled into your head.
C: Golgi Apparatus, I'm pretty sure, which packages things and sends it off.
D: Endoplasmic Reticulum: Creates proteins and helps with creating lipids and carbohydrates (I think) and also transports things.
So your answer would be B.
