Step 1: Recall the constitutional provision on quorum.
Article 100(3) of the Constitution states that the quorum to constitute a sitting of either House of Parliament shall be one-tenth of the total number of members of the House.
Step 2: Calculate for Lok Sabha.
The total strength of Lok Sabha is 543 elected members plus 2 nominated members = 545. One-tenth of 545 = 54.5, rounded up to 55, including the Speaker.
Step 3: Identify the correct answer.
The quorum required is 55 members including the Speaker.
\[ \boxed{55 \text{ members including the Speaker}} \]