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