The correct answer is option 'D' - All of the above.

Finance Commission:
The Finance Commission is a constitutional body established under Article 280 of the Indian Constitution. Its primary function is to recommend the distribution of financial resources between the central government and the state governments. The Finance Commission determines the share of taxes and other revenues that are to be allocated to the states from the divisible pool of central taxes. This mechanism restricts the financial autonomy of the states as it determines the amount of funds that the states will receive from the central government.

The office of CAG:
The office of the Comptroller and Auditor General (CAG) is an important constitutional mechanism provided for in Article 148 of the Indian Constitution. The CAG is responsible for auditing the accounts of the central and state governments. It ensures that the financial transactions of the government are carried out in accordance with the law and that public funds are used efficiently and effectively. The CAG submits its audit reports to the President or the Governor, who then places them before the Parliament or State Legislature respectively. The CAG's reports can have significant implications for the financial autonomy of the states as they highlight instances of financial mismanagement or irregularities, which may lead to reduced funding or increased scrutiny by the central government.

Financial emergency:
A financial emergency is a provision under Article 360 of the Indian Constitution. It empowers the President to proclaim a financial emergency in the country if he/she is satisfied that the financial stability or credit of India or any part thereof is threatened. During a financial emergency, the President can give directions to the states on matters related to financial management, including the reduction of salaries and allowances of government officials. This provision restricts the financial autonomy of the states as it allows the central government to exercise control over the financial affairs of the states.

In conclusion, all three mechanisms/provisions mentioned - the Finance Commission, the office of the CAG, and the financial emergency - restrict the financial autonomy of the states by either determining the allocation of funds, auditing the financial transactions, or allowing the central government to intervene in state financial matters.