Give it answer with proper explanation:

69. Consider the following (s) statements
I.   Pearl is obtained from oyster.
II.  Calcium carbonate is the main component of pearl. 
III. Rainbow coloured pearl is supposed to be the best pearl. 

Which of the statement (s) given above is/are correct?
(a) I, II and III              (b) II and III

(c) Only I                      (d) Only II

Dear student

Please refer the solution below for the said query

The correct option is a).
Pearls is obtained from oyster, a type of molluscs. 
When a parasite or any harmful substance enters the mantle cavity of the oyster, it starts secreting layers of calcium carbonate as a defence mechanism to protect itself from the intruder which are known as nacre. This secretion occurs many times and give rise to a pearl. So, colour of pearl depends on the type of oyster involved, thickness and layers of nacre, types of  intruders such as trace elements, zooplanktons, etc present in the surroundings. The rainbow coloured pearl is supposed to be the best pearl.



Hope this information clears your doubt about the topic.

Regards

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