Which of these is an example of positive-feedback regulation in the endocrine system?

Which of these is an example of positive-feedback regulation in the endocrine system?

A)           an increase in blood glucose causes an increase in insulin secretion; insulin moves glucose into cells

B)           an increase in TSH causes an increase in thyroid hormone secretion; thyroid hormones inhibit TSH secretion

C)           before ovulation, an increase in LH causes an increase in estrogen, which causes an increase in LH

D)           an increase in TRH causes an increase in TSH secretion; thyroid hormone inhibits TRH secretion

E)           an increase in blood calcium causes an increase in calcitonin secretion; calcitonin moves calcium into the blood.