could have been meaning

any fool can/could… if looks could kill… you cannot/could not but… you could have fooled me; could/might just as well… you could hear a pin drop; as far as the eye can/could see; I, you, etc. could use something; nothing could be further from the truth; you can/could do worse than do something; you could have knocked me down with a feather it must have been love chords