Consider the following statements.
1. The air standard efficiency of an Otto cycle is a function of the properties of the working substance (gas).
2. For the same compression ratio and same input, the thermal efficiency of an Otto cycle is more than that of a Diesel cycle.
3. The thermal efficiency of a Diesel cycle increases with decrease of cut-off ratio.
Which of the above statements are correct?
a) 1 and 2 only (b)1 and 3 only
(c) 2 and 3 only (d) 1, 2 and 3