To determine whether Gd-daa3 is selective for Zn2 , researchers compared relaxivity measurements of Gd-daa3 in the presence of different cations. Varying amounts of XCl2 (where X is Zn, Ca, or Mg) were added to a 0.1 mM solution of Gd-daa3 plus 10 mM KCl/10 mM HEPES buffer at pH 7.4. What is the most appropriate control for this experiment

2-bromo-2-methylbutane undergoes an e1 elimination reaction in the presence of ethanol. in the next reaction only one of the possible products is represented. although the product shown is not the major product of the reaction, notice that there is more than one way it can be produced. complete the mechanism and draw the missing substances.