Summarily, the passage is simply saying, if ones car is hit with eggs, it's best to wash it off immediately or risk re-doing the paint.
The sentences which highlight caution to the reader are:
The first sentence tried to quantify the amount of damage. The reader is able to evaluate the cost of damage eggs can do to a car;
The fourth and fifth sentences: urges parents not to encourage egg smashing on cars and goes on to highlight possible damages that can result from the same.
you have an opinion essay to exam? firstly, you have to focus on the Logic words to show your topic. Some Logic words will help you to write the topic quickly. Then, try to think about cool sentence to explain your topic and support your supporting idea. finally write your topic again within new words.