Which of the following best explain why the lower course of a river is sometimes choked with sediments? 1. The valley of a river is widest in its lower course. 2. The velocity of a river in its lower course is low. 3. The delta sometimes develops in a river's lower course. 4. Much of the river water is drawn for irrigation in the lower course. Select the correct answer using the code given below: [CDS 2011]