2) I (hear, am hearing, have been hearing) a strange noise.
3) I (did, have done, had done) a lot of work today.
4) I (smell, am smelling, have been smelling) something burning.
5) He used to visit us, but he (rarely comes, has rarely come) now.
6) My uncle (will arrive, will be arriving) tomorrow.
When to use the future tense “will” and the future continuous tense “will be … ing”.
7) The town (has been changing, had changed, has changed) its appearance completely since 1960.
8) We (have, are having) a lot of fun with the new video games.
9) I (knew, had known) him for several years before he took over the company.
1) “Abdul will be a doctor.” and “Abdul will become a doctor.” are both correct and mean the same thing, because both sentences are about the future.
2) The verb “hear”, like other verbs of perception, is not usually used in the continuous form. So if you are talking about the present, you say “I hear a strange noise.” and not “I am hearing a strange noise.”
However, the present perfect continuous tense “have been hearing” may be used in expressing the experience of someone suffering from hallucinations and who “has been hearing a strange noise” continuously for weeks or months.
3) You can say “I did a lot of work today.” (using the simple past tense of “do”), which means that you have finished working for today.
You can also say “I have done a lot of work today.”, which means that up to now you have done a lot of work today, but you may do more work today.
“Had done” is in the past perfect tense and cannot be used in your sentence, because your sentence doesn’t distinguish between two different times in the past.
4) The verb “smell” has no continuous form and so the correct sentence is “I smell something burning.”
5) The simple present tense “comes” is used because you are expressing a habitual occurrence that you have come to expect in the present, i.e. the rareness of his coming.
If you want to use the present perfect tense to express a similar idea, you may say, “He used to visit us, but recently he has only come once or twice.”
6) Both “My uncle will arrive tomorrow.” or “My uncle will be arriving tomorrow.” are correct. But the future continuous tense (“will be arriving”) indicates more certainty, i.e. that your uncle’s arrival is expected, because he has planned to arrive tomorrow.
The present continuous tense or the present tense can also be used to indicate the future when something has been planned, as in “My uncle is arriving tomorrow.” or “My uncle arrives tomorrow.”
7) “The town has changed its appearance completely since 1960.” is the correct sentence here.
If you use the present perfect continuous tense “has been changing”, you can’t use the word “completely” with it, because what is focused on in “has been changing” is the process of change, while “completely” suggests that no further change is possible. But you can say “The town has been changing its appearance since 1960.”
“Had changed” is a past perfect verb and can only be used to distinguish between two different times in the past. Your sentence in itself does not indicate another time in the past besides 1960.
But if the observation was made in the past, then “had changed” can be used, as in: “When I arrived in my hometown last week after an absence of 48 years, I could hardly recognise it. The town had changed its appearance completely since 1960.”
8) Because the video games are new, we should say “We are having a lot of fun with the new video games.” The fun seems to be going on now, and not habitually, when the simple present tense should be used, as in “We have a lot of fun with video games (not just new ones) every weekend.”
9) The correct sentence is: “I had known him for several years before he took over the company.” The sentence distinguishes between a period in the past when “I had known him” and an action in the more recent past when “he took over the company”. So a past perfect verb “had known” is used for the earlier period.