Chemical pollution will bring about a threat to agriculture and food chain, and ________ to human health.
While typing, Helen has a habit of stopping _____ to give her long and flowing hair a smooth.
The lawyer was expected to _____ some proposals after reading all those documents.
_____ his knowledge of the mountainous country, John Smith was appointed as our guide.
Political parties often differ in their views on various _____ concerning their own countries.
Evidence obtained from observation and experiment is often used to _____ a scientific theory.