<b><span style="color:#0000ff;">what are the differences between the following sentences in form and meaning?</span></b><br/><br/> a 1 What do you want?<br/> 2 Which do you want?<br/><br/><span style="color:#0000ff;">and what are the categories of "what" and "which"?</span><span style="color:#0000ff;"> and their functions?</span><br/><br/> b 1 They mustn’t think I’m interested.<br/> 2 They must think I’m not interested.<br/><br/> c 1 I’ll see Peter tomorrow.<br/> 2 I’ll be seeing Peter tomorrow<br/><br/> d 1 If in doubt, call the operator.<br/> 2 If you’re in doubt, you should call the operator.<br/><br/> e 1 I’ll do what I think is right.<br/> 2 I’ll do it, which I think is right.<br/><br/> f 1 She stopped looking for a way out.<br/> 2 She stopped to look for a way out.