The correct answer is D) Annular. The GE LM2500 gas turbine engine used in many Coast Guard vessels employs an annular combustor design. In an annular combustor, the fuel and air are mixed in an annular (ring-shaped) combustion chamber, which is more compact and efficient compared to other combustor designs. This annular configuration is commonly used in modern gas turbine engines due to its advantages in terms of size, weight, and performance. The other options are incorrect because a can-annular combustor has individual can-shaped combustion chambers arranged in an annular fashion, a can combustor has individual can-shaped chambers, and a cannular combustor is a hybrid design that combines features of can and annular configurations.