Octahedral complexes are coordination compounds that have an octahedral geometry, meaning they have six ligands arranged around a central metal ion. Tetragonal compression occurs when the ligands in the octahedral complex cause the metal-ligand bond lengths to become unequal, resulting in a distortion of the octahedral shape.

To determine which of the given complexes exhibits tetragonal compression, let's examine each option:

a) [CoCl2(NH3)4]
This complex has four ammonia (NH3) ligands and two chloride (Cl-) ligands arranged around the central cobalt (Co) ion. Since all the ligands are neutral and have similar sizes, there is no significant difference in the bond lengths, and the complex does not exhibit tetragonal compression.

b) KCuF3
This complex has three fluoride (F-) ligands and one potassium (K+) ligand arranged around the central copper (Cu) ion. The potassium ligand is larger than the fluoride ligands, resulting in a compression of the octahedral shape. This complex exhibits tetragonal compression.

c) KMnF3
This complex has three fluoride (F-) ligands and one potassium (K+) ligand arranged around the central manganese (Mn) ion. Similar to option a, the ligands in this complex are all neutral and have similar sizes, so there is no significant difference in the bond lengths. Thus, this complex does not exhibit tetragonal compression.

d) Both (a) and (c)
As explained above, option a does not exhibit tetragonal compression, while option c also does not exhibit tetragonal compression. Therefore, the correct answer is option b, KCuF3, which exhibits tetragonal compression.