To determine the distribution efficiency, we need to first calculate the average depth of water in the field. Once we have the average depth, we can compare it to the maximum depth to determine the efficiency.

1. Calculate the average depth:
- Add the depths of water in the field: 1.1 cm + 1.8 cm = 2.9 cm
- Divide the sum by the number of measurements: 2.9 cm / 2 = 1.45 cm

2. Compare the average depth to the maximum depth:
- The maximum depth is given as 1.8 cm.
- Calculate the efficiency by dividing the average depth by the maximum depth and multiplying by 100:
Efficiency = (1.45 cm / 1.8 cm) * 100 = 80.56%

3. Determine the distribution efficiency category:
- The correct answer is option 'D', which states that the efficiency is 75%.

Explanation:
The distribution efficiency is a measure of how evenly water is distributed across an area. In this case, the depths of water in the field are given as 1.1 cm and 1.8 cm. To calculate the average depth, we sum these two values and divide by the number of measurements (2). The average depth is found to be 1.45 cm.

Next, we compare the average depth to the maximum depth (1.8 cm) to determine the efficiency. By dividing the average depth by the maximum depth and multiplying by 100, we find that the efficiency is 80.56%.

However, the correct answer given is option 'D', which states that the efficiency is 75%. This suggests that there may be a mistake in the given options, as the calculated efficiency does not match any of them. Therefore, the correct efficiency value for this scenario cannot be determined based on the given options.