The half-life for the first-order reacion of HCl with ethylene is 15.4 s when the initial concentration of HCl is 0.67 M. What is the rate constant for this reaction? OPTIONS: A. 4.5 x 10^-2 B. 3.8 x 10^-2 C. 9.7 x 10^-2 D. 2.2 x 10^-2 E. 1.0 x 10^-2