专八词汇及练习题(17)

派生词汇 necessity n. 必要性，需要；[常用复数]必需品 necessitation n. 迫使，被迫 necessitous adj. 紧迫的；穷的，贫困的
13. colossal adj. very large 巨大的
e.g.: This is a colossal building.
派生词汇 colossus n. （pl. colossi） 巨像，巨人，巨物
14. deposit ①vt. to settle 沉积
e.g.: The Nile floods the fields and deposits mud on them.
②n. something deposited, especially by a natural process 沉积物
e.g.: Valuable mineral deposits have been found in this region.
派生词汇 depository n. 储藏室，存放处；受托人，保管人
15. silt ①n. sand, mud etc carried by flowing water and left at the mouth of a river, in a harbor, etc.淤泥
e.g.: The dam can prevent the deposit of silt.
②vi. to become filled with silt 被淤塞，使塞满泥沙
e.g.: The old channel has been silted up.
派生词汇 silty adj. 淤泥的，塞满了淤泥的
Exercise从以上单词中选出最恰当的词，填入空格内。
Purgatory is supposed to __1__you from your sins.
The Israeli army __2__for the Hamas bombing.
Human heart is an__3__ of the pump.
The astronauts had developed a __4__that was military in its rigidity.