<span>It sounds like he has post tramatic stress disorder from coming back from overseas. He would be recommend to take medicine and go to therapy to help him know how to get back into his regular family life. I'm sure it's extremely hard.</span>
Explanation:
Muscles act on joints antagonistically. Some muscles will contract while other contract pulling on bones around joint hence enabling movement. An example is the elbow joint is moved by antagonistic action of biceps and triceps. When your biceps contract and triceps relax you are able to bend your arm at your elbow. When your triceps contract and biceps relax, your arms straighten.
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The bark of a tree is impervious to gases and water because bark cells are dead cells of the epidermis and compactly arranged without intercellular spaces. They contain a chemical called suberin in their walls that make them impervious to gases and water and it doesn't allow gases or water into the tree as bark cells are in the bark outer most layer of the tree.
Crayfish are invertebrates which means they don't have a backbone. They are also arthropods, which means that they have a protective exoskeleton on the outside of their body. Other arthropods include insects, spiders, and centipedes. Crayfish continually shed their exoskeleton and regrow a new one. During this transition is when they are most vulnerable to predators because they aren't protected by their outer shell.
Crayfish are found all over the world in many different freshwater environments, such as rivers, creeks, springs, and swamps. But this doesn't necessarily mean that you will be able to find them. They are somewhat cryptic because they dig out homes for themselves under rocks and blend in well with their environment. Crayfish will ardently defend this dwelling against intruders using their strong front claws
True, a lot of cultivated fields use fertilizers that can be harmful to fish
