For a simple slope in Type C soil, 20 feet deep or less, what is OSHA's maximum allowable slope?

1. Vertical (0H:1V)
2. 3/4 horizontal to 1 vertical (3/4:1)
3. 1 horizontal to 1 vertical (1:1)
4. 1-1/2 horizontal to 1 vertical (1-1/2:1)