What is ‘simplification’ when referred to in drug development terms?

a) The process by which a drug candidate is synthesised as simply as possible

b) The process of adding more chiral centres to a compound to make it bind more easily to its biological target

c) The process of removing unimportant groups from a lead compound in the hope of maintaining activity but rendering the resulting compounds cheaper and easier to make

d) The process of shortening the drug development process from the discovery stage to its clinical trials stage