___ himself in carrying out an experiment, he can’t spare time to look after his children.
The gap between rural and urban education in China is widening, and education is the key to _____ rural problems.
The goods bought on line are _________ than those bought in stores.
Some Australian Aborigines still live in a similar way to their ancestors, while ______ live in cities, towns and the country in the same way _____ their fellow Australians.
The fleet made several expeditions _______ the exploration was stopped.
The Tibetans have lived in the Himalayas for centuries and have adjusted to the conditions _________.