Retired Moderator
Joined: 07 Jun 2014
Posts: 4813
Given Kudos: 0
WE:Business Development (Energy and Utilities)
Re: The new particles produced by CERN’s Large Hadron Collider a
[#permalink]
14 Oct 2017, 16:15
Explanation
Something lasting a millionth of a billionth of a billionth of a second is “very shortlived.” Ephemeral and fleeting have just this meaning. In real life, the particles may be small (infinitesimal), there may be a lot of them (myriad, countless), and they may bring a tear to the eye of a few scientists (poignant), but none of these are indicated by clues in the sentence.
Hence options ephemeral, fleeting are best fit!