It Is Difficult to Identify the Effects of Maternal Cocaine

It is difficult to identify the effects of maternal cocaine misuse 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 misusers 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 misuse and sudden infant death syndrome makes it impossible to conduct such research