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