I could crackle you could crackle he could crackle we could crackle you could crackle they could crackle
V-ing form
I could be crackling you could be crackling he could be crackling we could be crackling you could be crackling they could be crackling
Perfect
I could have crackled you could have crackled he could have crackled we could have crackled you could have crackled they could have crackled
V-ing perfect
I could have been crackling you could have been crackling he could have been crackling we could have been crackling you could have been crackling they could have been crackling
Negation
Simple form
I couldn't crackle you couldn't crackle he couldn't crackle we couldn't crackle you couldn't crackle they couldn't crackle
V-ing form
I couldn't be crackling you couldn't be crackling he couldn't be crackling we couldn't be crackling you couldn't be crackling they couldn't be crackling
Perfect
I couldn't have crackled you couldn't have crackled he couldn't have crackled we couldn't have crackled you couldn't have crackled they couldn't have crackled
V-ing perfect
I couldn't have been crackling you couldn't have been crackling he couldn't have been crackling we couldn't have been crackling you couldn't have been crackling they couldn't have been crackling
Interrogative form
Simple form
could I crackle? could you crackle? could he crackle? could we crackle? could you crackle? could they crackle?
V-ing form
could I be crackling? could you be crackling? could he be crackling? could we be crackling? could you be crackling? could they be crackling?
Perfect
could I have crackled? could you have crackled? could he have crackled? could we have crackled? could you have crackled? could they have crackled?
V-ing perfect
could I have been crackling? could you have been crackling? could he have been crackling? could we have been crackling? could you have been crackling? could they have been crackling?
Interro-negative form
Simple form
couldn't I crackle? couldn't you crackle? couldn't he crackle? couldn't we crackle? couldn't you crackle? couldn't they crackle?
V-ing form
couldn't I be crackling? couldn't you be crackling? couldn't he be crackling? couldn't we be crackling? couldn't you be crackling? couldn't they be crackling?
Perfect
couldn't I have crackled? couldn't you have crackled? couldn't he have crackled? couldn't we have crackled? couldn't you have crackled? couldn't they have crackled?
V-ing perfect
couldn't I have been crackling? couldn't you have been crackling? couldn't he have been crackling? couldn't we have been crackling? couldn't you have been crackling? couldn't they have been crackling?