These studies will yield valuable lemons ________.
A. in which to save lives and protect property
B. how to save lives and protect property
C. in how to save lives and protect property
D. about those to save lives and protect property
________ exposure to dirty air can cause people suffer from some diseases.
A. Raised
B. Prolonged
C. Expanded
D. Enlarged
The school offered flexible courses for farmers, ________ more hours of study when
A. with
B. without
C. in
D. for（
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