At what co2 concentration was stomata aperture width at its greatest? lowest ?

Stomata aperture width is at its greatest when there is low concentration of CO2 in the atmosphere.

As the air's CO2 content rises, many plants reduce their stomatal apertures. As a result, plants growing in CO2-enriched air typically reduce the density of stomates on their leaf surfaces and as a consequence, exhibit reduced rates of transpirational water loss, smaller productivity losses attributable to the indiscriminate uptake of aerial pollutants, and increased water-use efficiency.  

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a