Final answer:
To resize a picture to a specific height while maintaining the aspect ratio in PowerPoint, use the Picture Tools > Format > Lock Aspect Ratio option and adjust the height to 4 inches.
Step-by-step explanation:
To resize a picture to be 4 inches tall while allowing PowerPoint to automatically adjust the width to maintain the aspect ratio, you should use the following ribbon option: Picture Tools > Format > Lock Aspect Ratio and then manually enter the height of 4 inches. Once you lock the aspect ratio, changing one dimension (height or width) will automatically adjust the other dimension to keep the original proportion of the image. This ensures that the picture is not distorted after resizing. When you choose this option, PowerPoint will automatically adjust the width of the picture to maintain the aspect ratio, ensuring that the picture doesn't get distorted or stretched.