Final answer:
In a first-degree AV block, the P wave morphology is typically normal.
Step-by-step explanation:
In a first-degree AV block, there is a delay in conduction between the SA and AV nodes, resulting in an abnormally long PR interval on an ECG. The P wave morphology is typically normal in this type of block, meaning the shape and appearance of the P wave is not affected by the block.