It was wrong to cut down the old tree which dates back to 1915, _______ the reason.
The sunspot came into its active stage, ____ that happens once every eleven years.
The famous scientist, ____ a dinner party will be held tonight, is to arrive soon.
The driver could have survived, but he ____ the seat belt.
____ with a difficult situation, Mr Smith made up his mind ____ his boss for advice.
A bit more effort, I think, ____ the problem could be settled.