A study is planned of the relationship of maternal diabetes to the risk of a certain congenital malformation in the offspring. All of the following would argue for using a cohort design except:
a) The need for examining multiple outcomes over time.
b) The desire to establish temporality between maternal diabetes and congenital malformation.
c) The availability of a well-defined and accessible population with maternal diabetes.
d) The intention to identify rare outcomes in the offspring.