Cast iron piles. where can we use them choose from options:

Thank you for the invitation.

Between B and D.

I would go with D.are useful for heavy vertical loads.

Answer D they are useful for heavy vertical loads 

D is the right answer........

I agree with answers D .....................

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Agree with experts 

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D

A.are suitable for works under sea water

Thanks for invitation , but unfortunately this is not my field.