I can’t help, can you explain what we should include in the essay and what we have to answer.
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
The answer is A, a cell wall
Answer:
Because the vaccine is an antigen from living, weakened or killed microorganisms that activate the immune system and the body produces protective antibodies.
Answer:
The fix nitrogen into free nitrogen which is a usable form. They also bring nitrogen back into the system by decomposing dead organisms.
Answer 2.
Because, they are known as nitrogen fixing bacteria. These organisms convert nitrogen in the soil to ammonia, which can then be taken up by plants. After nitrogen has been fixed, other bacteria convert it into nitrate, in a process known as nitrification.
Both answer is correct choose the best choice for you.
Hope this helps!
