At no time, as we know, _______ forget that solving Taiwan Issue is entirely internal Chinese affair.

At no time, as we know, _______ forget that solving Taiwan Issue is entirely internal Chinese affair.

At no time, as we know, _______ forget that solving Taiwan Issue is entirely internal Chinese affair.

1. A.
   we can
2. B.
   we could
3. C.
   can we
4. D.
   could we

At no time, as we know,          forget that solving Taiwan Issue is entirely internal Chinese affair.

A．we can          B．we could         C．can we          D．could we