1. The elastic critical stress in compression increases with decrease in slenderness ratio.
2. The effective length depends on the boundary condition at the end of column.
3. The elastic critical stress in compression is independent of the slenderness ratio.
4. The ratio of effective length to its least radius of gyration is called as slenderness ratio.

The True statements are:

i) 2 and 3 ii) 3 and 4 iii) 2,3,4 iv) 1,2,4

The true statements are the option iv) 1,2,4.

Statement 3 is wrong because the elastic critical stress in compression is dependent of the slenderness ratio.