The correct options are
B When a member is disqualified.
C When a member voluntarily resigns by writing a letter to the Presiding officer.
D When a member remains absent from the Parliament sessions for more than 60 days without permission.
The seats can fall vacant in the Parliament. This can happen in multiple ways. 1) If a member voluntarily resigns by writing a letter to the Presiding Officer of the House. 2) If a member remains absent from the Parliament sessions for more than 60 days, without permission. The third situation which leads to vacancy of seats is related to disqualification of members.