Consider the following statements in respect of critical flow in a wide rectangular channel: 1. The specific energy is minimum for a given discharge. 2. The discharge is maximum for a given specific energy 3. The specific force is minimum for a given discharge. 4. The Froude number is equal to unity. Which of these statements are correct? (a) 1 , 2 & 3 only (b) 1, 2, 3 & 4 (c) 1, 2 & 4 only (d) 2, 3 & 4 only