Select ‘the incorrect statement from the following pertaining to design of a graded filter -
1
To avoid segregation, filter should contain particles of size larger than 75 mm.
2
For proper working, the filter material should not contain more than 5% of fines passing 75 micron IS sieve
3
The material of the last layer should be coarse enough not be carried away through the openings of the perforated pipes.
4
None of these
5
Question Not Attempted