During World WarⅡ, Japan attacked Pearl Harbor without declaring war _____ America.
Those black clouds are a sure _____ that it’s going to rain.
She raised her finger to her lips as _____ for silence.
Shortly after the accident, _____ police were sent to the spot to keep order.
We already have ______ pencils, but we need two ______ pens.
Jim is ______ person, and everyone is willing to be ______ with him.