The subject
A loud noise woke me up.
What woke you up?
Shakespeare wrote Romeo and Juliet.
What did Shakespeare write?
The dog bit the cat.
Who did the dog bite? (Object)
Someone wrote this book
Who wrote this book?
I saw someone at the mall.
Who did you see at the mall
The storm broke the window.
What broke the window? (Subject)
Something happened last night.
What happened last night?
I bought a very expensive watch.
What did you buy?
The red bus goes to the airport.
What bus goes to the airport? (Subject)
Someone called the police.
Who called the police?
The chef prepared the daily special.
What did the chef prepare?
I want the blue shirt.
Which shirt do you want? (Object)