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