Algae used for the manufacture of iodine is
A. Nostoc
B. Laminaria
C. Polysiphonia
D. Diatoms

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Hint:Iodine is an essential biologically important element. Iodine is a key component for the synthesis of a growth-regulating hormone called thyroid hormone. The brown algae also called kelp produces iodine which can be used in various economically important productions.

Complete answer:Iodine is an important biologically essential element. It is a major constituent of thyroid hormones. A brown algae species or Phaeophyceae also called kelp is cultivated for iodine. It belongs to the Laminaria genus. The alga has long, leathery laminae. It is relatively large in size. Products like algin and mannitol are also isolated from Laminaria. Commercially it is known as brown seaweed. It is majorly found in the Northern Pacific Ocean and North Atlantic Ocean. They prefer colder ocean water where there are rocky shores. It is cultivated using the floating raft method. The young Laminaria sporophytes stay attached to ropes.
Laminaria has various other medicinal applications. This includes dilation of the cervix for labor induction and surgical procedures. As it produces iodine it benefits to promote thyroid health. Laminaria also shows antitumor activity. It is also used in improving the enzymatic processes of the intestine. It is an active study subject in today’s medical field.
Laminaria species shows a characteristic property of absorbing heavy metals. Many species are now being studied to be used in clearing heavy metals from the wastewaters.

So, option B is the right answer.

Note: Iodine deficiency leads to scarcity of thyroid hormones. This may lead to swelling of thyroid tissue. This condition is named as goiter. It can be cured by restoring iodine levels and surgical procedures if needed. For this purpose, Laminaria finds huge medicinal applications.