Conjugación del verbo inglés
COULD STIFFEN

Verbo regular: stiffen - stiffened - stiffened

Afirmación

Forma simple	Forma con V-ing
I could stiffen you could stiffen she could stiffen we could stiffen you could stiffen they could stiffen	I could be stiffening you could be stiffening she could be stiffening we could be stiffening you could be stiffening they could be stiffening
Perfecto	Perfecto con V-ing
I could have stiffened you could have stiffened she could have stiffened we could have stiffened you could have stiffened they could have stiffened	I could have been stiffening you could have been stiffening she could have been stiffening we could have been stiffening you could have been stiffening they could have been stiffening

Negación

Forma simple	Forma con V-ing
I couldn't stiffen you couldn't stiffen she couldn't stiffen we couldn't stiffen you couldn't stiffen they couldn't stiffen	I couldn't be stiffening you couldn't be stiffening she couldn't be stiffening we couldn't be stiffening you couldn't be stiffening they couldn't be stiffening
Perfecto	Perfecto con V-ing
I couldn't have stiffened you couldn't have stiffened she couldn't have stiffened we couldn't have stiffened you couldn't have stiffened they couldn't have stiffened	I couldn't have been stiffening you couldn't have been stiffening she couldn't have been stiffening we couldn't have been stiffening you couldn't have been stiffening they couldn't have been stiffening

Forma interrogativa

Forma simple	Forma con V-ing
could I stiffen? could you stiffen? could she stiffen? could we stiffen? could you stiffen? could they stiffen?	could I be stiffening? could you be stiffening? could she be stiffening? could we be stiffening? could you be stiffening? could they be stiffening?
Perfecto	Perfecto con V-ing
could I have stiffened? could you have stiffened? could she have stiffened? could we have stiffened? could you have stiffened? could they have stiffened?	could I have been stiffening? could you have been stiffening? could she have been stiffening? could we have been stiffening? could you have been stiffening? could they have been stiffening?

Forma interro-negativa

Forma simple	Forma con V-ing
couldn't I stiffen? couldn't you stiffen? couldn't she stiffen? couldn't we stiffen? couldn't you stiffen? couldn't they stiffen?	couldn't I be stiffening? couldn't you be stiffening? couldn't she be stiffening? couldn't we be stiffening? couldn't you be stiffening? couldn't they be stiffening?
Perfecto	Perfecto con V-ing
couldn't I have stiffened? couldn't you have stiffened? couldn't she have stiffened? couldn't we have stiffened? couldn't you have stiffened? couldn't they have stiffened?	couldn't I have been stiffening? couldn't you have been stiffening? couldn't she have been stiffening? couldn't we have been stiffening? couldn't you have been stiffening? couldn't they have been stiffening?