The Government of India Act, 1919, also known as the Montagu-Chelmsford Reforms, brought several significant changes in the administrative structure of British India. Let's evaluate each statement in relation to the Act:

1. Decentralization was provided for the first time: 
   This statement is incorrect. The concept of decentralization was introduced earlier through the Government of India Act, 1861, which allowed for the establishment of legislative councils in provinces.
2. Bicameral legislature introduced in India for the first time: 
   This is the correct statement. The Government of India Act, 1919, introduced a bicameral legislature at the central level for the first time in India, consisting of the Council of State and the Legislative Assembly.
3. Communal representation was provided for the first time: 
   This statement is incorrect in the context of the 1919 Act because communal representation was actually introduced earlier in the Indian Councils Act of 1909 (also known as the Morley-Minto Reforms), which granted separate electorates to Muslims.
4. It introduced Civil service in India for the first time: 
   This is incorrect. The modern civil service in India began with the establishment of the Covenanted Civil Service under the East India Company's Charter Act of 1833, and was later formalized with further acts before 1919.

Based on the analysis of each statement, the most appropriate and correct statement regarding the provisions of the Government of India Act, 1919, is that it introduced a bicameral legislature in India for the first time.