GRAS stands for Generally Recognized as Safe. In the regulatory sense, this designation means that experts have reviewed the evidence on a substance's safety for its intended use in foods and, based on that consensus, it can be used without requiring pre-market approval as a food additive. The key idea is recognition by qualified scientists of safety, not merely that someone regards it as safe or that it’s globally recognized. It’s a U.S.-focused term tied to the FDA framework, and while there can be self-affirmed or FDA-notified GRAS determinations, it does not imply worldwide regulation or approval of substances.

Focus on how much of the total liquid in Emma’s recipe is water and use a proportion. You identify the total volume of liquid the recipe makes and the fraction that is water, then multiply total liquid by that fraction. For example, if the recipe yields 1,000 ml in total and water accounts for 14% of it, you calculate 1,000 × 0.14 = 140 ml. So the amount of water in Emma’s recipe is 140 ml, which matches the given data. If the total volume or the water fraction were different, you’d adjust the calculation by using the same method.

Iodine is essential for making thyroid hormones. The thyroid gland cannot produce T3 and T4 without iodide; it actively takes up iodide, incorporates it into the hormone structure, and then releases the hormones into circulation. When iodine is insufficient, thyroid hormone production drops, leading to hypothyroidism and often a goiter as the gland tries to compensate. Adequate iodine allows normal hormone synthesis, while potassium, sodium, and iron aren’t directly used to build thyroid hormones, so they’re not the mineral most closely tied to thyroid function.

Gluten avoidance is essential in celiac disease. The key idea is that foods containing gluten—wheat, barley, and rye—trigger an autoimmune response that damages the small intestine. A pulled pork sandwich is typically served on bread or a bun made from wheat, so it brings gluten into the meal. The pork itself is naturally gluten-free, but the bread makes the whole dish unsafe for someone with celiac disease. The other options are generally gluten-free: grilled chicken and rice, without gluten-containing sauces or ingredients, is safe; a fresh fruit salad contains no gluten; yogurt is usually gluten-free unless a flavored or mixed product includes gluten-containing additives. So the reason this choice is the one to avoid is the gluten in the bread.