After reading the paragraph below, answer the questions that follow.
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.
According to the data, this remediation plan is most effective with which element?
◦ copper (Cu)
◦ zinc (Zn)
◦ cadmium (Cd)
◦ lead (Pb)