Which one of the following pairs of organs includes only the...

In vertebrate body the glands may be classified on the basis of presence or absence of ducts, ie, exocrine and endocrine glands. The secretions of exocrine glands are carried by ducts to a particular organ for some metabolic activity, eg, salivary glands, liver. The endocrine glands have no ducts and their secretions get absorbed into the immediate surrounding blood circulation to reach the specific organs to initiate a particular metabolic change, eg, thyroid, parathyroid, adrenal, thymus. The glands, which have dual functions (ie, secretion of hormones and some other functions) are called heterocrine glands, $\mathrm{eg}$, pancreas, testes, ovaries.