The correct answer is: A. Perpendicular to the bank.
Attracting groynes are built perpendicular to the bank to protect the bank from erosion. They are made of wood, stone, or concrete, and they extend out into the water. The groynes trap sediment, which helps to build up the bank and protect it from erosion.
Groynes are also used to control the flow of water in rivers and streams. They can be used to prevent flooding, or to improve the navigation of a waterway.
Groynes are an important part of coastal engineering, and they are used all over the world to protect coastlines from erosion.
B. Inclined down stream is incorrect because groynes are built perpendicular to the bank, not inclined down stream. This would not be effective in protecting the bank from erosion.
C. Inclined up stream is incorrect because groynes are built perpendicular to the bank, not inclined up stream. This would not be effective in protecting the bank from erosion.
D. None of these is incorrect because the correct answer is A.