Answer:
I'm not quiet sure if you're supposed to add words when correcting or adjusting the sentences, but here's what makes the most sense to me:
1. After his puppy learned to sit and roll over, Walter entered him in a local dog show.
2. No one was happier than Alex after he discovered his missing wallet while mowing the lawn.
3. Everyone warned the child not to get close to the house because a dog that snarled all the time was there.
4. Getting carsick is common when driving down a winding road.
I hope this helps!
