Insulin is produced by which of the following?

Select the correct option for the following statements:
$(i)$ The pancreas is a $heterocrine$ / $endocrine$ gland.
$(ii)$ $Muscular$ $tissue$ / $Neural$ $tissue$ is a composite tissue.

Diabetes mellitus is caused due to the deficiency of insulin, which is secreted by:

In the pancreas,the secretion of pancreatic juice and hormones is performed by:

The hormone glucagon:

$A$ sample of urine was diagnosed to contain a high content of glucose and ketone bodies. Based on this observation, answer the following:
$(a)$ Which endocrine gland and hormone is related to this condition?
$(b)$ Name the cells on which this hormone acts.
$(c)$ What is the condition called and how can it be rectified?