B. Wh-words are what, when, where, who, which, why and how. We use clauses with a wh- word. (e.g. What are you doing?)
a. We use who to ask questions about people. (e.g. Who is that? Who lives here? Who did you see?)
b. use whose to ask about possession. (e.g. Whose coat is this? or Whose is this coat? Whose book is that? or Whose is that book? Whose bags are those? or Whose are those bags?)
c. use what to ask questions about things. (e.g. What is that? What do you want?)
d. use which to ask someone to choose something. (e.g. Which came first, the chicken or the egg? I’ve got two books. Which do you want?)
e. can also use what and which with nouns. (e.g. What subjects did you study at school? What newspaper do you read? Which newspaper do you read – the Times or the Guardian? Which book do you want? Which one is yours?)
B1. after verbs of thinking: know, understand, suppose, remember, forget, wonder (e.g. I know where you live.) We also use clauses with if. (e.g. I wonder if we’ll see Peter.)
a. after verbs of saying: ask, say, admit, argue, reply, agree, mention, explain, suggest (e.g. I asked what she wanted.)
b. tell and some other verbs of saying must always have a direct object: tell, remind (e.g. We tried to tell them what they should do.)
c. after some verbs of thinking and saying we use wh-words and the to-infinitive. (e.g. We didn’t know what to do.)
d. When the subject of the to-infinitive is the same as the subject of the main verb. (e.g. He didn’t know what to do -> He didn’t know what he should do)
e. When the subject of the to-infinitive is the same as the person spoken to. (e.g. Nobody told me what to do. -> Nobody told me what I should do.)
f. after some nouns to say more about the noun. (e.g. Is there any reason why I should stay?)
g. We often use a wh-clause after is. (e.g. I missed my bus. That’s why I was late.)