Which drugs cause birth defects?.

Choice A rationale: A Placebo is a substance that has no therapeutic effect and is used as a control in clinical trials. It does not cause birth defects. Choice B rationale: Carcinogens are substances capable of causing cancer in living tissue, not specifically birth defects. Choice C rationale: Steroids can have side effects and risks, but they are not specifically known to cause birth defects. Choice D rationale: Teratogens are substances that can cause birth defects. This includes certain medications, chemicals, infectious diseases, and physical conditions.