It Is Difficult to Identify the Effects of Maternal Cocaine

It is difficult to identify the effects of maternal cocaine abuse on pregnancy because

A) the last wave of cocaine abuse peaked in the late 1990s, leaving little motivation for foundations to fund research in this area.
B) most pregnant cocaine abusers also abuse other compounds known to affect fetal growth and development.
C) the infants tend to suffer from sleep apnea following birth, which alters cognitive function.
D) the close association between maternal cocaine abuse and sudden infant death syndrome makes it impossible to conduct such research.