In a balanced ecosystem, the number of deer would be:
a) greater than the number of producers
b) less than the number of carnivores
c) equal to the number of scavengers
d) none of the above

Option D

Explanation:

In a balanced ecosystem, the flow of resource, food and energy must be adequate enough to fulfill the requirement of all.  

In case if the population of deer is higher than the population of producers then the producers would not be able to meet out the requirement of herbivore deer. Hence, this option is incorrect

In case if deer population is less than the population of carnivores, all the carnivores will not be able to get sufficient food. Hence, this option is also incorrect

Option C is also not feasible as equal number of scavengers will not be able to degrade the large biomass of dead animals and plants.  

Hence, option D is correct

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c