The correct answer is A. 2 members.
A quorum is the minimum number of members that must be present at a meeting in order for the meeting to be valid. The quorum for a general meeting of a private company which is a subsidiary of a public company is 2 members. This is because the Companies Act 2006 states that the quorum for a general meeting of a private company is 2 members, unless the articles of association provide otherwise. The articles of association of a private company may provide for a higher quorum, but they cannot provide for a lower quorum.
Option B is incorrect because the Companies Act 2006 does not specify a quorum of 3 members for a general meeting of a private company which is a subsidiary of a public company.
Option C is incorrect because the Companies Act 2006 does not specify a quorum of 5 members for a general meeting of a private company which is a subsidiary of a public company.
Option D is incorrect because the Companies Act 2006 does not specify a quorum of 7 members for a general meeting of a private company which is a subsidiary of a public company.