Correct only FIVE of the given sentences (knowledge of languages "aid"; the ambassador with his family "invite"; "sit in the CSS examination"; "whether or not"; "Aslam and me plan"; "If some of you make a noise, they shall be punished"; "enquire what is the salary"; "too tired that").

Corrected sentences

1. His knowledge of languages and international relations aids him in his work. (The subject is "knowledge", which is singular; "languages and international relations" belongs to the "of" phrase.)

2. The ambassador, with his family and staff, invites you to a reception at the embassy on Tuesday afternoon. (A phrase introduced by "with" does not make the subject plural.)

3. This year, he will sit for (or appear in) the CSS examination. (The idiom is "sit for an examination"; "sit in" means to attend as an observer.)

4. The Chief Executive will let us know whether he can attend the meeting. ("Or not" is unnecessary after "whether" here, though "whether or not" is not wrong. Since the sentence is acceptable as printed, it is the one to leave out.)

5. When he comes back from vacation, Aslam and I plan to look for another apartment. ("Aslam and I" is the subject; the plan is in the present, so the time clause takes the present tense.)

6. If any of you make a noise, you will be punished. ("Any" suits a condition; "they" does not match "you", and "will", not "shall", expresses a plain future for the second person.)

7. He came to me to enquire what the salary attached to the appointment was. (An indirect question takes statement word order, and the tense moves back after "came".)

8. I am so tired that I cannot look up words and idioms in my English book. ("Too" pairs with "to": "too tired to look up"; "so" pairs with "that". "Hunt words" should be "hunt for" or "look up".)

Tip

When a verb follows a long subject, cross out the phrases between them ("of languages and international relations", "with his family and staff") and read subject and verb together.