Underline the correct word, then try to explain the idioms.

1 Let’s put on some music. It’s as silent/quiet as the grave in here.
2 He’s got food poisoning and he’s been as sick as a dog/cat all week.
3 Don’t worry about Maggie; she’s as tough as old shoes/boots.
4 The Martin children are not at all alike. They’re as different as chalk and cheese/milk.
5 I’ll look after Jo anytime. Really, she’s as good as silver/gold.
6 Ben can’t wait to get started on the project. He’s as keen as ketchup/mustard​