I could boast you could boast he could boast we could boast you could boast they could boast
V-ing form
I could be boasting you could be boasting he could be boasting we could be boasting you could be boasting they could be boasting
Perfect
I could have boasted you could have boasted he could have boasted we could have boasted you could have boasted they could have boasted
V-ing perfect
I could have been boasting you could have been boasting he could have been boasting we could have been boasting you could have been boasting they could have been boasting
Negation
Simple form
I could not boast you could not boast he could not boast we could not boast you could not boast they could not boast
V-ing form
I could not be boasting you could not be boasting he could not be boasting we could not be boasting you could not be boasting they could not be boasting
Perfect
I could not have boasted you could not have boasted he could not have boasted we could not have boasted you could not have boasted they could not have boasted
V-ing perfect
I could not have been boasting you could not have been boasting he could not have been boasting we could not have been boasting you could not have been boasting they could not have been boasting
Interrogative form
Simple form
could I boast? could you boast? could he boast? could we boast? could you boast? could they boast?
V-ing form
could I be boasting? could you be boasting? could he be boasting? could we be boasting? could you be boasting? could they be boasting?
Perfect
could I have boasted? could you have boasted? could he have boasted? could we have boasted? could you have boasted? could they have boasted?
V-ing perfect
could I have been boasting? could you have been boasting? could he have been boasting? could we have been boasting? could you have been boasting? could they have been boasting?
Interro-negative form
Simple form
could I not boast? could you not boast? could he not boast? could we not boast? could you not boast? could they not boast?
V-ing form
could I not be boasting? could you not be boasting? could he not be boasting? could we not be boasting? could you not be boasting? could they not be boasting?
Perfect
could I not have boasted? could you not have boasted? could he not have boasted? could we not have boasted? could you not have boasted? could they not have boasted?
V-ing perfect
could I not have been boasting? could you not have been boasting? could he not have been boasting? could we not have been boasting? could you not have been boasting? could they not have been boasting?