The term "anionic sphere complex" refers to a complex ion that carries a net negative charge. To identify an anionic sphere complex among the options provided, we need to look at the complex ions and see which ones are negatively charged. Option A: Hexaamminecobalt(III) chloride. This complex is [Co(NH3)6]3+ and carries a net positive charge. Therefore, it is not an anionic sphere complex. Option B: Potassium hexacyanoferrate(II). This complex is [Fe(CN)6]4, which carries a net negative charge. Therefore, it is an anionic sphere complex. Option C: Tetraamminedichlorocobalt(III) ion. This complex ion is [Co(NH3)4Cl2]+, which carries a net positive charge. Thus, it is not an anionic sphere complex. Option D: Pentaamminechlorocobalt(III) sulphate. This complex itself is [Co(NH3)5CI]2+ and carries a net positive charge. So, it is not an anionic sphere complex. The correct answer is Option B: Potassium hexacyanoferrate(II), which features the anionic complex [Fe(CN)6]4−.