4. In normal phase HPLC, a. the mobile phase is polar and the stationary phase is nonpolar. b. the mobile phase is nonpolar and the stationary phase is polar. c. eluent strength is increased by adding a more polar solvent to the mobile phase. d. eluent strength is increased by adding a less polar solvent to the mobile phase. 5. Resolution is proportional to the A. number of theoretical plates in a column B. square root of the number of theoretical plates in a column C. square of the number of theoretical plates in a column D. cube root of the number of theoretical plates in a column