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