1. The problem asks to identify which labelled angles among a, b, e, f, and g on two triangular prisms are right angles. 2. A right angle measures exactly 90 degrees. 3. Typically, in a triangular prism, the angles on the triangular faces can be right angles if the triangle is a right triangle. 4. For the left prism, angles a and b are on the triangular face. If the triangle is right-angled, one of these could be 90 degrees. 5. For the right prism, angles e and f are on the triangular face, and g is on the end face. The end face is usually rectangular, so angle g is likely a right angle. 6. Without exact measurements, the best assumption is that angle g is a right angle because it is on the rectangular end face. 7. Angles a, b, e, and f are on triangular faces and may or may not be right angles depending on the triangle type. 8. Therefore, the labelled right angle is angle g. Final answer: angle g is a right angle.