I could assemble you could assemble she could assemble we could assemble you could assemble they could assemble
V-ing form
I could be assembling you could be assembling she could be assembling we could be assembling you could be assembling they could be assembling
Perfect
I could have assembled you could have assembled she could have assembled we could have assembled you could have assembled they could have assembled
V-ing perfect
I could have been assembling you could have been assembling she could have been assembling we could have been assembling you could have been assembling they could have been assembling
Negation
Simple form
I couldn't assemble you couldn't assemble she couldn't assemble we couldn't assemble you couldn't assemble they couldn't assemble
V-ing form
I couldn't be assembling you couldn't be assembling she couldn't be assembling we couldn't be assembling you couldn't be assembling they couldn't be assembling
Perfect
I couldn't have assembled you couldn't have assembled she couldn't have assembled we couldn't have assembled you couldn't have assembled they couldn't have assembled
V-ing perfect
I couldn't have been assembling you couldn't have been assembling she couldn't have been assembling we couldn't have been assembling you couldn't have been assembling they couldn't have been assembling
Interrogative form
Simple form
could I assemble? could you assemble? could she assemble? could we assemble? could you assemble? could they assemble?
V-ing form
could I be assembling? could you be assembling? could she be assembling? could we be assembling? could you be assembling? could they be assembling?
Perfect
could I have assembled? could you have assembled? could she have assembled? could we have assembled? could you have assembled? could they have assembled?
V-ing perfect
could I have been assembling? could you have been assembling? could she have been assembling? could we have been assembling? could you have been assembling? could they have been assembling?
Interro-negative form
Simple form
couldn't I assemble? couldn't you assemble? couldn't she assemble? couldn't we assemble? couldn't you assemble? couldn't they assemble?
V-ing form
couldn't I be assembling? couldn't you be assembling? couldn't she be assembling? couldn't we be assembling? couldn't you be assembling? couldn't they be assembling?
Perfect
couldn't I have assembled? couldn't you have assembled? couldn't she have assembled? couldn't we have assembled? couldn't you have assembled? couldn't they have assembled?
V-ing perfect
couldn't I have been assembling? couldn't you have been assembling? couldn't she have been assembling? couldn't we have been assembling? couldn't you have been assembling? couldn't they have been assembling?