Concept: Article 356 deals with President's Rule in a State when there is failure of constitutional machinery.
Step 1: Understand Article 356.
If the President is satisfied that the government of a State cannot be carried on according to the Constitution, a proclamation under Article 356 may be issued.
\[
\text{Article 356} = \text{President's Rule}
\]
Step 2: Understand parliamentary approval.
A proclamation under Article 356 must be approved by both Houses of Parliament within two months from the date of issue.
\[
\text{Approval period} = 2 \text{ months}
\]
Step 3: Select the correct option.
Therefore, the correct answer is 2 months.