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