A flat character is someone is unchanging throughout the story, in other words, the character is Stagnent.
C. A heavy rainstorm.
The text shows indication of a storm arriving. “Clouds arrived” are an indicator that clouds quickly appeared. “Lightning flashed” tells us these are storm clouds. It makes sense that next it would start raining, making the next event a heavy rainstorm.
In the first sentence, the "he" is a nominative as it is a subject.
In the second sentence it is an object as the form "me" is actually "I", but "i" is a nominative form and "me" is an objective form.
In the third sentence "Us" is also used in objective form as "us" is an object of an action by "my sister".