This is our contribution to ________ world of the 21st century, ________ world of independence and mutual understanding.
The government __________ air quality in urban areas from level one to five : excellent,fairly good, slightly polluted, poor and dangerous.
I got __________ from my classmates when climbing the hill.
The teacher __________ his students __________ five groups.
The police are trying to find out the __________ of the woman killed in the traffic accident.
—Who knows where Terry is? —The reason __________ Terry is absent is __________ his father had an accident.