That is the conclusion of a new study that looked at how respiratory(呼吸道) viruses _____ on airplanes. 句子缺少的单词的词性是什么? Prior to the new study, little was known about the risks of getting _____ infected by common respiratory viruses, such as the flu or common cold, on an airplane, the researchers said. 谓语动词是哪个呢?以及句子缺少的单词的词性。