Explanation:

- Section 126 of the Evidence Act grants professional privilege, protecting communications between a legal advisor and their client.

- Option 1: For the purposes of professional employment - This is valid as it covers communication made for professional legal advice.

- Option 2: In the course of employment - This is also valid as it includes communications exchanged in the routine process of legal employment.

- Option 3: Both (a) & (b) - This is correct as the professional privilege applies to both the purposes of professional employment and in the course of such employment.

- Option 4: Neither (a) nor (b) - This is incorrect as both conditions apply.