Answer:
(1) Nitrite poisoning
(2) Its cause is elevated levels of nitrite in the pond or culture system water.
A virus is not a bacteria, but it is caused by a bacteria. A virus causes the immune system to weaken.
It is all of them. To be alive we all kind of have to have a face or body, we all need cells to help us with our day to day activities and we all need to communicate with other humans so that would be social behavior.
False negative is a condition when you got a negative result for a specimen which was positive. To prevent false negative occur, first you need to use golden standard test or a test with high specificity. You can do multiple tests to ensure the specimen is negative and using a positive control to make sure the reagent is still working fine.