Where are the Islets of Langerhans found?

"Islets of Langerhans" are found in

Which of the following are the symptoms of hypersecretion of insulin?
$I$. Hypoglycemia $II$. Sweating $III$. Irritability $IV$. Glycosuria
Select the correct combination:

Assertion $(A):$ Insulin is a hypoglycemic hormone.
Reason $(R):$ Insulin increases the cellular uptake and utilisation of glucose.

$..............$ acts mainly on the liver cells and stimulates glycogenolysis resulting in hyperglycemia.

Failure of insulin production results in