Which of the Following Statements in a Research Abstract or Article

Which of the following statements in a research abstract or article identifies "gaps" in knowledge?

A) "Comparing the same individuals at ages 13 and 23, O'Malley and Bachman (1983) reported an increase in self-esteem."
B) "While 39% of people on the kidney waiting list are from a minority racial group, only 23% of deceased donor organ recipients are from the same group."
C) "Although grandparents are increasingly a focus in the literature on ageing and older adults, very little attention has been given to experiences of grandfathers caring for grandchildren, with the experiences of men of colour in these roles receiving the least consideration."
D) "A significant portion of the morbidity and mortality associated with coronary heart disease is related to patient delay in seeking treatment for symptoms of acute coronary syndrome (ACS) ."