sick 生病的；有病的
①作"生病的"讲时可作表语和定语。
②在句中作表语时be sick=be ill.
③feel sick感到恶心
④be sick of厌倦......
ill生病的；有病的
①作"生病的"讲时只作表语，不作定语。
②ill的比较级和最高级分别为worse,worst.
③ill的名词形式为illness.
e.g. Mary can't come today because she is sick/ill.
玛丽生病了，所以今天不能来了。
I have to look after my sick grandpa.
我得照顾生病的爷爷。（此时不能用ill)
I want to get off the bus. I feel a little sick.
我想下车，我感到有点恶心。
I am sick of rope skipping.
我厌倦了跳绳。
－Why doesn't Lucy go to school today?
－She has to take care of her________father.
A.sick
B.ill
C.illness
D.healthy
解析：考查词义辨析。作"生病的"讲时，sick 可作定语修饰名词，ill只能作表语。illness为名词，healthy 可作定语，根据答句句意"她得照顾生病的父亲"可知答案为A。
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