To determine the rock types that form in the semi-isolated barred basin shown, we need to understand the order of precipitation due to evaporative mechanisms in sedimentary environments.

In such settings, the sequence of mineral precipitation is primarily driven by the solubility of minerals in water. As evaporation progresses, minerals that are less soluble will precipitate first, followed by those that are more soluble. Here’s the sequence:

1. Carbonates (such as calcite and aragonite) are the least soluble and will precipitate first. Thus, they form in the region marked by A, closest to the water source.
2. Gypsum is more soluble than carbonates and less soluble than halite. It will precipitate after carbonates, hence forming in region B.
3. Halite (common salt) is quite soluble and precipitates last in the sequence as the water becomes more saline. It forms in region C, furthest from the initial water source.

Therefore, the appropriate rock types that form in regions A, B, and C are:

• A – Carbonates
• B – Gypsum
• C – Halite

This sequence aligns with the typical evaporative processes observed in a barred basin setting.