Match each phylum with the correct description cnidarians
internal skeletons made of hardened plates
echinoderms
radial symmetry and stinging cells
arthropods
jointed body parts and an external skeleton
annelids
segmented body and closed circulatory
system

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.