Final answer:
Common advice to pregnant women includes avoiding alcohol and nicotine. With regard to a developing fetus, these two substances are examples of Teratogens (option a)
Step-by-step explanation:
With regard to a developing fetus, the two substances that pregnant women are advised to avoid, alcohol and nicotine, are examples of teratogens. A teratogen is any environmental agent, whether biological, chemical, or physical, that can cause damage to the developing embryo or fetus. Alcohol can lead to a range of fetal alcohol spectrum disorders (FASD), which includes physical defects such as small head size and abnormal facial features, developmental delays, and cognitive issues such as low IQ and poor impulse control. Nicotine, found in cigarette smoke, is similarly harmful as it crosses the placenta and can affect the fetus, often leading to reduced growth and other serious health issues.
Hence, the answer is option a.