In the Lok Sabha, a quorum refers to the minimum number of members required to be present in the House for the proceedings to be valid. According to Article 100 of the Indian Constitution, the quorum to constitute a sitting of the House is one-tenth of the total number of members of the Lok Sabha, including the Speaker.

To ensure that there is a quorum present, the Speaker of the Lok Sabha has various methods at their disposal. One common method is to count the heads of the members at the beginning of every day's first session. This is mentioned in option 1 of the given question.

However, it should be noted that this is not the only method used by the Speaker to ensure the presence of quorum. The Parliamentary Secretariat, which is responsible for the administration and logistics of the Parliament, also keeps a watch on the attendance of the members in the House and informs the Speaker if the quorum is not present. This is mentioned in option 2 of the given question.

In addition to these methods, the attendance register kept at the entrance of the Lok Sabha is also monitored to ensure that the members are present. Option 3 of the given question refers to this method.

Overall, while option 1 is a commonly used method by the Speaker to ensure quorum, it is not the only method used. Option 2 and option 3 are also correct methods, and the Speaker may use any of these methods to ensure that there is a quorum present in the Lok Sabha.