What's the marking system in IGNOU? What's meant by A,B,C,D?

The marking system of IGNOU is as follows:

Grade A = 80%-89%
Grade B = 70%-79%
Grade C = 60%-69%
Grade D = 50%-59%
Grade E = 40%-49%
Grade F = 0-39%

Grade O = 90%-100%

Physiotherapy / Stroke exercise for 18 month Part-II

Sachin Ramesh Tendulkar "master blaster "