What is Tom … now?

 Has he already … his homework?

 I … done my homework, when he came.

 He showed me the book, which he … .

buys;  
had bought; 
buying.

  When I entered the room, Nick … reading a book.  

 are;
 is;
 was.

 What … the Houses of Parliament like?

  do;
 is;
 are.

 Last year he … to London.

This work is … than that one.

 easy;
 the easiest;
 easier.

this is his book, and that book is … .  

 … came in.