I could sneeze you could sneeze he could sneeze we could sneeze you could sneeze they could sneeze
V-ing form
I could be sneezing you could be sneezing he could be sneezing we could be sneezing you could be sneezing they could be sneezing
Perfect
I could have sneezed you could have sneezed he 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 he 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 he 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 he 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 he 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 he 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 he sneeze? could we sneeze? could you sneeze? could they sneeze?
V-ing form
could I be sneezing? could you be sneezing? could he be sneezing? could we be sneezing? could you be sneezing? could they be sneezing?
Perfect
could I have sneezed? could you have sneezed? could he 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 he 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 he 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 he 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 he 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 he have been sneezing? couldn't we have been sneezing? couldn't you have been sneezing? couldn't they have been sneezing?