The biomass pyramids for phytoplankton and trees in their respective environments are

The right answer is opposite.

In the air, the biomass of primary producers is often much higher than the biomass of consumers, especially in forests where a large part of the biomass is wood. In aquatic environments and especially oceanic, the biomass of primary producers (phytoplankton) is generally lower than that of consumers but this biomass is rapidly renewed.

a.) a destruction fo cells by viral reproduction