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 could not pick you could not pick he could not pick we could not pick you could not pick they could not pick
V-ing form
I could not be picking you could not be picking he could not be picking we could not be picking you could not be picking they could not be picking
Perfect
I could not have picked you could not have picked he could not have picked we could not have picked you could not have picked they could not have picked
V-ing perfect
I could not have been picking you could not have been picking he could not have been picking we could not have been picking you could not have been picking they could not 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
could I not pick? could you not pick? could he not pick? could we not pick? could you not pick? could they not pick?
V-ing form
could I not be picking? could you not be picking? could he not be picking? could we not be picking? could you not be picking? could they not be picking?
Perfect
could I not have picked? could you not have picked? could he not have picked? could we not have picked? could you not have picked? could they not have picked?
V-ing perfect
could I not have been picking? could you not have been picking? could he not have been picking? could we not have been picking? could you not have been picking? could they not have been picking?