Question

A region’s photosynthetic productivity is influenced most significantly by

Answer 1

A region's photosynthetic productivity is influenced most significantly by A) availability of nutrients and amount of solar radiation. 
There are two most important things when it comes to photosynthesis of plants in a certain region on Earth. 

Answer 2

A region's photosynthetic productivity is influenced most significantly by : A. Availability of nutrients and amount of solar radiation

Photosynthetic productivity  cannot happen without enough nutrients and radiation. In this photosynthetic productivity, the plants will process the nutrients it gathered and process it into producing its own food

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