Plants Are Sometimes Used for Phytoremediation in Areas Where the Soil

Plants are sometimes used for phytoremediation in areas where the soil has been contaminated with heavy metals. Suppose the Acme Remediation Company is proposing to remediate a contaminated area that you wish to restore. Acme presents you with the following data as evidence of their company's ability to remediate soil.

-The CEO of Acme Remediation Company is always trying to improve the company's effectiveness by keeping up with current research. Which research topic should have the highest priority for that research?

A) comparison of plant species' tolerance of clay versus sandy soils
B) comparison of plant species' ability to live in dry versus moist soils
C) comparison of plant species' tolerance of heavy metals in soils
D) comparison of plant species' bioaccumulation of metal ions