Account for the observations highlighted below: (You may use appropriate illustrations or mechanisms, but in either case, be brief and to the point) (3 Marks Each) (a) Ring closing metathesis is more versatile for macrocarbocyclization than cycloaddition reactions. (b) Boronate esters are more effective in carbon-carbon bond formations with aryl halides than organocuprates. (c) Organozinc compounds react with ketones, but do not react with esters.