最长的.单词的词根有：
pneumono-(of lung 肺的)
ultra-(beyond 越过)
micro-(very small 极小的)
scopic-(of viewing or observing 观察或注意的)
silico-(of silicon 硅的)
volcano-(mountain that releases fire and ash 火山的)
coni-(koni,of dust 尘土的)
osis-(forming the name of a disease 表示疾病)