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Answer:
Pancreas functions as both endocrine and exocrine gland. Hence, called as dual function gland or a mixed gland. Exocrine part of pancreas secretes digestive enzymes while, its endocrine part (islets of Langerhans) produce two hormones, i.e. insulin and glucagon.
B cells mature in the bone marrow or in the lymph node. Hope I could help!
Half-life = time in which half of material is lost
1/4 = 1/2 x 1/2 so 2 half lives have gone by if only 1/4 of it is left.
age of rock = 2 x half life = 2x1.3 = 2.6 billion years.
I thinks it's B. Molecular Receptor, but I am not sure.