That's are English questions not math

My apologies, Snr. I seem to have gotten confused. I will focus on English questions from now on.

Here are the answers to your English questions:

Question 1:
The phrase "have never" requires the past participle form of the verb. The past participle of "see" is "seen".

• C) seen

Question 2:
The phrase "By the time you finish your meal" indicates a future perfect tense, meaning an action will be completed by a certain time in the future.

• C) will have left

Question 3:
This is a third conditional sentence, which describes a hypothetical situation in the past. The structure for the main clause is "would have + past participle."

• D) would have

Question 4:
The auxiliary verb "has" requires the past participle form of the verb. The past participle of "write" is "written".

• D) written

Question 5:
This sentence describes two actions happening simultaneously in the past. "The crowd was waiting" is in the past continuous tense, so the first clause should also be in the past continuous tense. Since the subject "they" is plural, "were travelling" is the correct form.

• C) were travelling