Statement-I is false. The first attempt at an All-India Census was conducted in 1872 during the tenure of Lord Mayo, but it was not a complete or synchronous census covering all territories. The first complete and synchronous decennial census across British India was held in 1881. Statement-II is true. Starting from 1881, decennial censuses became a regular practice in India and have continued uninterrupted till 2011. Statement-III is false. According to census data, the urban population in India was 18% by 1940.