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