Which of the following statements are correct with respect to Mohr- Coulomb failure criteria on soils.

I: Mohr failure envelope is approximated as straight line but in actual, it is curved.

II: Mohr failure envelope is approximated as a curved line but in actual, it is straight.

III: The Mohr circle drawn for soil cannot cross the Mohr failure envelope.

IV. Cohesion c and angle of internal friction φ are fundamental properties of soil and are independent of testing conditions.