—Can you work out the problem? —I can’t ______your explain how to do it.
He returned home safe and sound after a fierce battle, ____ was unexpected.
____ we is known to all, English is not very difficult to learn.
The old man had three sons, all of ____ died during World War Ⅱ.
I have bought two pens, ____ write well.
Do you know the reason ____ she has changed her mind?