Select all the correct statements about pile necking.

i. Pile necking is generally acceptable as it does not affect the structure of a building.

ii. Pile necking does not happen when steel piles are used.

iii. Pile necking may happen when the casing was retracted above the concrete being placed.

iv. Pile necking is caused by a pile being squeezed by soil because the lateral pressure from the soil is greater than the wet concrete mixture.

v. Pile necking is a disadvantage of driven piles.