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

• A. 10
• B. 5
• C. 25
• D. 50

Answer: (A)

Fetal tissues are highly radiosensitive, and deterministic (dose‑dependent) effects have a clear threshold. During early development, rapid cell division and organ formation mean that even small amounts of ionizing radiation can disrupt growth, cause malformations, or lead to fetal loss. In animal studies, deleterious effects to the embryo/fetus have been observed at doses around 10 rads (about 0.1 Gy). This makes 10 rads the smallest dose among the options that is known to produce such effects in these experiments, whereas lower doses are less likely to cause the endpoints studied, and higher doses would also cause harm but are not the minimal dose required for observable adverse outcomes.