What is the correct term for low levels of oxygen in a body of water?

Four types of motile cells in human body?

Nasa scientists must work together to make sure that everything is correct and accounted for when launching a shuttle. besides a physicist, what other type of scientist would be in making sure that the shuttle has the appropriate type and amount of fuel to reach its destination?

Which best describes the digestive system of arthropods? a incomplete, two openings b complete, one opening c two-way, one opening d one-way, two openings