A、Bad breath. B、Excessive sweating. C、Breathing difficulty. D、High blood pressure. A题目问短文说水分流失的负面影响是什么。短文提到，温度过高会导致水分流失，而水分流失经证明

Sunshine and high temperatures can mean picnics and parks and trips to beaches, but they can make your body react in some strange ways. First, sunshine can actually affect your breath. You may think that summer is the perfect time to go on a date or chat with an attractive boy or girl, but excessive heat can cause you to lose water, which has been proven to have a pretty unattractive side effect—bad breath. When you are lacking water, your mouth becomes dry. Bacteria accumulate because there isn’t enough water in your mouth to wash it away. Sunshine can stop you from sweating too. The body’s normal temperature is 36-37° C, but if it heats up to 40-41° C, you may find yourself getting heat stroke. At that point, your heat regulatory system can essentially quit, which stops you from sweating as your body tries to keep water around your vital organs. However, the sun can have a positive influence on your body by raising your energy levels. You might feel like the sun is giving you extra energy for your day, which is actually happening. And vitamin D from sunshine can help your body to absorb certain minerals, which are linked to building stronger bones. Therefore, I suggest you spend more time in the park with your friends, but make sure you apply lots of skin protection, and fill up those water bottles too.
    19. What does the passage say about hot sunshine?
    20. What does the passage say is a negative side effect of water loss?
    21. What is said to be a positive effect of sunshine?