Answer:
Tornadoes form when warm, humid air collides with cold, dry air
Explanation:
 
        
                    
             
        
        
        
Imperative sentences usually end with a period but can occasionally end with an exclamation point. These sentences are sometimes referred to as directives because they provide direction to whomever is being addressed. 
Below, you'll find some examples of imperative sentences. Note that each line is issuing a command of some sort. 
Pass the salt.
Move out of my way!
Shut the front door.
Find my leather jacket.
Be there at five.
Clean your room.
Complete these by tomorrow.
Consider the red dress.
Wait for me.
Get out!
Make sure you pack warm clothes. 
Choose Eamonn, not Seamus.
Please be quiet.
Be nice to your friends.
Play ball!
        
                    
             
        
        
        
Miss Stephanie Crawford crossed the street to tell the latest to Miss Rachel. Miss Maudie bent over her azaleas. It was summertime, and two children scampered down the sidewalk toward a man approaching in the distance. The man waved, and the children raced each other to him.
It was still summertime, and the children came closer. A boy trudged down the sidewalk dragging a fishingpole behind him. A man stood waiting with his hands on his hips. Summertime, and his children played in the front yard with their friend, enacting a strange little drama of their own invention.
It was fall, and his children fought on the sidewalk in front of Mrs. Dubose’s. The boy helped his sister to her feet, and they made their way home. Fall, and his children trotted to and fro around the corner, the day’s woes and triumphs on their faces. They stopped at an oak tree, delighted, puzzled, apprehensive.
Winter, and his children shivered at the front gate, silhouetted against a blazing house. Winter, and a man walked into the street, dropped his glasses, and shot a dog.Summer, and he watched his children’s heart break. Autumn again, and Boo’s children needed him.
<span>Atticus was right. One time he said you never really know a man until you stand in his shoes and walk around in them. Just standing on the Radley porch was enough.</span>
        
             
        
        
        
“When Caitlyn is with Tyler all of her problems seem to disappear. But as things get serious, she discovers Tyler's jealous side. Once she realizes her "perfect" boyfriend is as controlling as he is caring, Caitlyn is faced with a choice: she can either let this relationship define her, or find the courage to break away” (Goodreads)