The primary characteristic of wastewater from the tannery operation is:

The primary characteristic of wastewater generated from tannery operations is often associated with high salinity, elevated levels of biochemical oxygen demand (BOD), and significant amounts of suspended solids. Tanning processes frequently involve the use of various chemicals and organic matter, leading to wastewater with a complex chemical composition that includes not only high BOD but also high concentrations of salts from the tanning agents used.

BOD is a measure of the organic material in wastewater and indicates the potential for oxygen depletion in receiving waters. In tanneries, the presence of high BOD signifies that there is a substantial amount of organic waste that could impact aquatic life if discharged without treatment. The high suspended solids are due to physical particles and residues from animal hides and other materials used during the tanning process.

Other characteristics like low pH levels or high temperatures may occur in some cases but are not as universally dominant as the combination of high salts, BOD, and suspended solids. These factors make option C the most accurate representation of the wastewater's primary characteristics from tannery operations.