A. Bradycardia, constipation, and hypotonia are common symptoms associated with congenital hypothyroidism due to the reduced metabolism that results from decreased thyroid hormone levels. B. Elevated serum T3 and T4 would not be expected in congenital hypothyroidism; these levels are typically low. C. Tachycardia, diarrhea, and tremors are more indicative of hyperthyroidism, not hypothyroidism. D. In congenital hypothyroidism, the thyroid-stimulating hormone (TSH) is typically elevated as the body attempts to stimulate the thyroid gland to produce more hormones.