Wignall calculated the "killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava that they produced. He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.
    The main idea of this paragraph is__________.
    A、Killing Power of Ancient Volcanic Eruptions
    B、Accounting for the Killing Power of Older Eruptions
    C、Calculation of the Killing Power of Older Eruptions
    D、A Mass Extinction
    【正確答案】 C
    【答案解析】 本段第一句話是說：Wignall calculated the "killing efficiency" for these volcanoes…；Wignall 計算了這些火山的“滅絕效率”……；其中killing efficiency與killing Power意思差不多，屬于同義詞轉(zhuǎn)換，因此選擇B或C，但是account for 意思是：(在數(shù)量方面)占；說明(原因等)不符合句意，因此不選擇B。