Highest annual net primary productivity is of:
a. Tropical deciduous forest
b. Temperate evergreen forest
c. Temperate deciduous forest
d. Tropical rainforest

Hint: The net amount of element carbon which is assimilated after the process of photosynthesis and autotrophic respiration over a given period of time is known as the Net Primary Productivity. The abbreviation form of Net Primary Productivity is NNP. In general, the Net Primary Productivity is represented by the units such as kg /ha /year (that is annual NPP or ANPP).

Complete answer:
The net primary productivity of the Tropical rain forest is 190 to 380 metric tons per hectare. The energy which is said to be stored at the producer level in an ecosystem is called primary productivity. In terms of per unit area per year, the highest value of the net primary of a forest ecosystem is highest in the tropical rainforest.

The energy which is said to be stored at the consumer level in an ecosystem is called secondary productivity. The rate of photosynthesis is called gross primary productivity.

The rate of storage of organic matter excluding the utilized for respiration by plants is called Net primary productivity. The rate of storage of organic matter which is not used by the consumers is called net production.

The annual net primary productivity of Temperate deciduous forest and Temperate evergreen forest is 160 to 280 metric tons per hectare. The net primary productivity of Tropical deciduous forest is 90 to 380 metric tons per hectare.

Hence, the correct answer is option (D).

Note: One can also define the term net primary productivity as the amount of carbon dioxide vegetation taken by the plants in the duration of photosynthesis minus the amount of carbon dioxide released by the plants in the duration of respiration after metabolizing sugars and starches for energy. That is carbon dioxide absorbed by the green plants – carbon dioxide released by the green plants in an ecosystem. Approximately 170 billion tons is the value of the annual net primary productivity of the whole biosphere. The ocean's contribution is of the value of 55 billion tons out of 170 billion tons.