The calibration curve below shows the plots of absorbance for standard solutions against the concentration of lead ions in part per million (ppm) Absorbance 0.7 0.6 0.5 0.4 0.3 0.2 སྦྱི 8 3 5 38; 0.1 0 1 2 3 5 Lead (Pb) Concentration (ppm) Lead Calibration Curve The concentration of lead in unknown soil sample can be determined at the MOST accurate if it is between. O A. 1.0 and 5.0 ppm O B. 0.0 and 5.0 ppm O C. 1.0 and 4.0 ppm O D. 0.0 and 4.0 ppm

Method of Analysis Solve y′′ − 4y′ + 3y = et/(1 + et) using the method of variation of parameters.

number 2 ONLY

12-atoms at grain boundaries are ------chemically reactive than grains .themselves • less more • equal none 13-A reversible changes in an atomic structure of the metal with a corresponding change in the properties of steel, is called • poly-tropic • allotropic critical point none of these 14-What types of bonding would you expected of nylon (primary composed from hydrogen and carbon)? • covalent bonds van der Waals • hydrogen • ionic • 1 and perhaps 2 choices