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