Please check my sentences againﾂ　ﾂ（Nov. 24 version)

Dear naive English speakers,
would you kindly check my sentences again?

1) I know that your father speaks three languages fluently.

2) My mother says that she wants to go to India.

3) My grandfather believes that I will be a famous singer.

4) My mother asked me if I wanted a new bike.

5) I wonder if Mike needs a car.

6) Do you know who that tall man is?

7) I wonder how far we have walked.

8) I asked my brother why he bought this machine.

9) He said that this is necessary for his work.

10) He believes that the machine will be very useful.

11a) I wonder if the machine will be useful.
11b) I wonder whether the machine will be useful.

12) I know what I should do now.

Thanks in advance.

Hirashin

5 could be right in certain context. It makes it sound as if the person might not have a car. Which if the speaker is unsure if the person has a car or not, it would be correct. If the speaker knows that Mike has a car, but the car may need to be replaced, it might be something like "I wonder if Mike needs a new car." It just really depends on what you meant for that sentence. Number 9 is also correct in certain situations. For example if you were showing the item that is necessary for his work. But it makes it sound as if the work is not finished yet. If that is the case that is fine, if not you should replace is with was. Which would mean that the work is finished. For some reason the word that in the first three sentences sounds odd to me. I am not sure if it is incorrect or not and I am unsure why it sounds odd. Maybe it is just me.

The word "that" in the first three is absolutely correct. They just sound odd to you because relative pronouns often can be dropped in English.

Thank you for the help, Ootmaster and Mike. I appreciate it.

Mike, "that" in the first three sentences is not a relative pronoun but a subordinate conjunction. But
that's not a problem. What I want to know is not a grammatical term but whether native speakers
use those sentences or not.

Hirashin

I personally wouldn't use it that way. But there are people that would. It is a way that a native speaker might say it though.

I know there are many native English speakers that will use sentences 1-3.

Thanks for the help, Clark.

Hirashin