On the one hand, we should make efforts to improve the economy ; on the other hand, we must keep a balance between ___________ development and environmental protection.
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Some successful people managed to gain _______and fortune even though they dropped out of school.
A(n) _________ is a very small piece of matter with a negative electrical charge, found in all atoms.
The ________ bombs, also known as nuclear bombs , would cause disasters if they were used in the wars.
I never felt anxious or _________when somebody else got a higher position or made a lot of money.