Option 1: After the first reading: This option is incorrect. After the first reading of the bill, it is usually taken up for the second reading and not sent to a select committee.

Option 2: After the second reading: This option is incorrect. After the second reading, the bill is usually taken up for clause-by-clause consideration and discussion, and not sent to a select committee.

Option 3: After general discussion during the second reading: This option is incorrect. The general discussion during the second reading is meant to give MPs an opportunity to express their views on the bill, but it does not necessarily lead to the bill being sent to a select committee.

Option 4: At any stage at the discretion of the Speaker: This option is correct. The Speaker has the authority to refer a bill to a select committee at any stage of its consideration in Parliament. This is often done when further examination and study of the bill by a select committee is deemed necessary.