根据下列句子所给汉语意思或提示，写出空缺处单词的正确形式。
小题1:Scientists are ________ (调查) into the cause of cancer.
小题2:To get the job done, one should be ________(精力充沛) and hardworking.
小题3:As a ______（奖赏）for passing her exams, she got a new bike from her parents.
小题4:Dilma Rousseff, who won 56% of the _______ (选票), was elected President of Brazil.
小题5:The old lady likes (spy) into other people’s affairs.