【编者按】威廉希尔app 英语四六级频道为大家收集整理了“英语四级考试词汇活记活用”供大家参考，希望对大家有所帮助!
1,Lung cancer, like some other cancers, often doesn’t produce ________ until it is too late and has spread beyond the chest to the brain, liver or bones.
A) trails
B) therapies
C) symptoms
D) symbols
■题目相关单词解释(提示:最好做完题目再看):■
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
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
■题目相关单词解释(提示:最好做完题目再看):■
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
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
■题目相关单词解释(提示:最好做完题目再看):■
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
4,It is clear that the dog has a much greater ________ of its brain devoted to smell than is the case with humans.