a) Shell and tube Heat exchanger
b) Plate heat exchanger
c) Finned tube heat exchanger
d) Plate fin heat exchanger

Answer: a
Explanation: Shell and tube Heat exchanger is used in oil refineries and is appropriate for high pressure applications. The hydraulic fluids and the oils in the engines are cooled by using this exchanger. It comprises a number of tubes attached inside a cylindrical shell. The two fluids can transfer the heat where one fluid flows inside the tubes and other fluid flows over the tubes.