1.Lung cancer, like some other cancers, often doesn’t produce ________ until it is too lateand has spread beyond the chest to the brain, liver or bones.
A) trails
B) therapies
C) symptoms
D) symbols
2.With the increasing unemployment rate, workers who are 50 to 60 years old are usually the first to be ________.
A) laid off
B) laid aside
C) laid out
D) laid up
3.The physical differences between men and women can be ________ directly to our basic roles as hunters and child-bearers.
A) pursued
B) traced
C) switched
D) followed
4.It is clear that the dog has a much greater ________ of its brain devoted to smell than is the case with humans.
A) composition
B) compound
C) percent
D) proportion
5.American college students are increasingly ________ with credit card debt and the consequences can be rather serious.
A) boosted
B) burdened
C) discharged
D) dominated
第一题：
trail:n. 踪迹,小径,尾;v. 拖,尾随,追踪
therapy:n. 治疗
symptom:n. 病症，症候，征兆，表征
symbol:n. 象征，符号，标志
第二题：
lay off:解雇;停止做
lay aside:把...搁置一旁;储存
lay out:安排,布置;摆出,展开
lay up:使卧床不起
第三题：
pursue:v.追捕,追求,继续从事
trace:n. 踪迹，痕迹；vt. 跟踪，追踪;追溯,探索;临摹
switch:n. 开关，突然转变；v. 改变，交换
follow:vt. 跟随，追赶，沿着…前进，仿效；vi. 跟随，紧接
第四题：
devote:vt. 将…奉献(给)，致力于
composition: n. 作文,著作,组织
compound:n. 混合物,复合字;a. 复合的,混合的,合成
percent: n. 百分比,百分数
proportion:n. 比例，率，份儿，部分，均衡，调和；vt. 使成比例，使均衡
第五题：
increasingly:ad. 日益地，愈加地
consequence:n. 结果，后果
boost:n. 推进,支援;v. 推进,提高
burden:n.重负,负荷;重担v.使负重,装载;加重压于,烦扰
discharge:v. & n. 排出，放出，允许…离开，释放，放电
dominate:vt. 支配的，统治，控制，高出于，居高临下；vi. 居支配地位，处于最重要的地位
