Energy independence" and its rhetorical (修辭的) companion "energy security" are, however, slippery concepts that are rarely though through.
出自-2014年6月閱讀原文
This slippery slope of eroding ethics and bigger risks leads only to disaster.
出自-2011年12月閱讀原文
The company spent the last five years developing solar panels that are only about a quarter of an inch thick and are strong enough to stand up to heavy highway traffic without breaking or making the roads more slippery.
2017年12月四級(jí)真題（第二套）聽力 Section A
They calculated that rolling the block required about as much force as moving it along a slippery path.