Mapping an image to a sub-sentence can be done with a little trick in InVideo. Here are the steps to do the same:
Step 1: Go to the 'Advanced Editing' screen.
Step 2: By moving the pointer below your scene, find out when your text changes from one sub-sentence to the next.
Step 3: Using the seek bar change the time of the images in the scene.
Here is a tutorial to help you better understand the process: