English verb conjugation
COULD PREHEAT

Regular verb: preheat - preheated - preheated

Affirmation

Simple form	V-ing form
I could preheat you could preheat he could preheat we could preheat you could preheat they could preheat	I could be preheating you could be preheating he could be preheating we could be preheating you could be preheating they could be preheating
Perfect	V-ing perfect
I could have preheated you could have preheated he could have preheated we could have preheated you could have preheated they could have preheated	I could have been preheating you could have been preheating he could have been preheating we could have been preheating you could have been preheating they could have been preheating

Negation

Simple form	V-ing form
I couldn't preheat you couldn't preheat he couldn't preheat we couldn't preheat you couldn't preheat they couldn't preheat	I couldn't be preheating you couldn't be preheating he couldn't be preheating we couldn't be preheating you couldn't be preheating they couldn't be preheating
Perfect	V-ing perfect
I couldn't have preheated you couldn't have preheated he couldn't have preheated we couldn't have preheated you couldn't have preheated they couldn't have preheated	I couldn't have been preheating you couldn't have been preheating he couldn't have been preheating we couldn't have been preheating you couldn't have been preheating they couldn't have been preheating

Interrogative form

Simple form	V-ing form
could I preheat? could you preheat? could he preheat? could we preheat? could you preheat? could they preheat?	could I be preheating? could you be preheating? could he be preheating? could we be preheating? could you be preheating? could they be preheating?
Perfect	V-ing perfect
could I have preheated? could you have preheated? could he have preheated? could we have preheated? could you have preheated? could they have preheated?	could I have been preheating? could you have been preheating? could he have been preheating? could we have been preheating? could you have been preheating? could they have been preheating?

Interro-negative form

Simple form	V-ing form
couldn't I preheat? couldn't you preheat? couldn't he preheat? couldn't we preheat? couldn't you preheat? couldn't they preheat?	couldn't I be preheating? couldn't you be preheating? couldn't he be preheating? couldn't we be preheating? couldn't you be preheating? couldn't they be preheating?
Perfect	V-ing perfect
couldn't I have preheated? couldn't you have preheated? couldn't he have preheated? couldn't we have preheated? couldn't you have preheated? couldn't they have preheated?	couldn't I have been preheating? couldn't you have been preheating? couldn't he have been preheating? couldn't we have been preheating? couldn't you have been preheating? couldn't they have been preheating?