Answer:
Option D
Explanation:
First of all, the compound has a complex positive part "$[Co(H_{2}O)_{4}(NH_{3})_{2}]^{3+}"$ therefore, according to IUPAC conventions, the positive part will be named first. Secondly, in writing the name of the complex, ligands are named first in alphabetical order, irrespective of their charge, hence "ammine" will be written prior to "aqua".