Aforest contains both spruce trees and pine trees. young spruce trees need shade in order to mature. young pine trees need full sunlight in order to mature. how do spruce trees most likely affect the environment's carrying capacity for pine trees?
a. spruce trees reduce the sunlight available to young pine trees, thus decreasing the environment's carrying capacity for pine trees.
b. spruce trees young pine trees adapt to growing in shade, thus increasing the environment's carrying capacity for pine trees.
c. spruce trees prevent other trees from competing with pine trees, thus increasing the environment's carrying capacity for pine trees.
d. spruce trees encourage the growth of other trees that need sunlight, thus decreasing the environment's carrying capacity for pine trees.

A. Spruce trees reduce the sunlight available to young pine trees, thus decreasing the environment's carrying capacity for pine trees.  

Explanation:

Carrying capacity is the maximum number of the members of the population of a species which an ecosystem can sustain in terms of availing the resources. The population size will be affected when the carrying capacity does not meet the demand of the population.  

In the given situation, the pine trees requires the sunlight to mature whereas the spruce trees requires the shade to get mature. If the spruce trees are taller than the pine trees they are likely to reduce the available sunlight of the young pine trees. Hence, the environmental carrying capacity for pine trees will decrease in the absence of proper sunlight.

i have to report this, it doesn't relate to biology

"d.) carbon dioxide and hydrogen sulfide"