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