Consider the following statements in respect of an S.I. engine:
1. The maximum speed occurs when the fuel mixture is about 10% richer than the stoichiometric value.
2. An increase in compression ratio decreases the flame speed.
3. An increase in intake temperature increases the flame speed.
Which of the statements given above are correct?
(a) 1 and 2 only (b) 2 and 3 only
(c) 1 and3 only (d) 1, 2 and 3