Final answer:
Research supports the correlation between maternal smoking during pregnancy and an increased risk of ADHD, while evidence for sugar, television, and food additives is not as strong or is not supported.
Step-by-step explanation:
The correlation between environmental factors and Attention Deficit Hyperactivity Disorder (ADHD) supported by research specifically points to maternal smoking. Studies such as those conducted by Thakur et al. (2013) suggest that maternal smoking during pregnancy is associated with an increased risk of ADHD in offspring. The research evidence is less conclusive or not supported for other factors such as an excess of sugar, overexposure to television, and food additives.