For animal experiments it is estimated that as little as ______ rads delivered to the embryo/fetus can cause deleterious effects.

• A. 5 rads
• B. 10 rads
• C. 25 rads
• D. 50 rads

Answer: (B)

Radiation sensitivity of the embryo/fetus is high because cells are rapidly dividing and organs are forming, so even small energy deposits can disrupt development. In animal experiments, deleterious developmental effects—such as growth retardation or malformations—have been observed at doses around 10 rads (about 0.1 Gy). This is the smallest dose among the options that reliably produces harm in these studies. Lower doses, like 5 rads, are less consistently associated with such effects, while higher doses (25 or 50 rads) would cause more obvious damage but aren’t the lowest threshold for harm.