ANS:C - Titanium

The most suitable material of construction for condenser tubes, where the cooling medium is brine (salty water), is Titanium. Explanation:

1. Aluminium: While aluminium has good corrosion resistance in many environments, it is not well-suited for use in condenser tubes where the cooling medium is brine. Brine (salty water) can lead to accelerated corrosion of aluminium, potentially causing pitting and other forms of corrosion.
2. Copper: Copper is often used in condenser tubes due to its excellent thermal conductivity and corrosion resistance. However, copper may not be the best choice when the cooling medium is brine, as it can be susceptible to corrosion in salty environments.
3. Titanium: Titanium is highly resistant to corrosion, including corrosion from brine and other corrosive environments. It has excellent corrosion resistance in seawater and brine, making it an ideal choice for condenser tubes in marine and salty water applications.
4. Stainless Steel: While certain types of stainless steel can offer good corrosion resistance, they may not provide the same level of protection against corrosion from brine as titanium. Stainless steel can be susceptible to corrosion in certain environments, including those containing chloride ions found in brine.