The system is a complex network of glands that release tiny amounts of hormones into the bloodstreams of humans and other vertebrate animals.

The endocrine system is a complex network of glands that release tiny amounts of hormones into the bloodstreams of humans and other vertebrate animals.

Explanation:

The endocrine system is a set of organs, tissues and cells whose function is to release various chemical substances called hormones into the bloodstream. The endocrine glands are the group of cells that produce and release hormones, which are secreted into the blood while waiting for the proteins that are designed to specifically capture each of them, are responsible for transporting them to the cells of the tissues and organs to which they must reach. Once there, they transmit the precise orders to regulate cellular activity.

answer: the correct option is d. enzyme

lactase and carbonic anhydrase are the examples of enzymes.

lactase is an enzyme, which is present in the small intestine of mammals. it in the digestion of the disaccharide, lactose ( milk sugar) by converting it into two monosachharide, which are glucose and galactose.

carbonic anhydrase is present in the red blood cells. this enzyme plays significant role in the transport of co₂. it in the conversion of co₂ and h₂o into carbonic acid, which is then dissociated into bicarbonate ions and hydrogen ions.