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People have always been curious ______ how living things on the earth exactly began.

A.in                      B.at                      C.of                             D.about

People have always been curious      how living things on the earth exactly began.

   A. in            B. at                C. of            D. about

People have always been curious      how living things on the earth exactly began.

   A. in            B. at                C. of            D. about

people have always been curious ______ how living things on the earth exactly began.

   A. in        B. at       C. of      D. about

 People have always been curious           how living things on the earth exactly began.

        A. in               B. at               C. of                   D. about

people have always been curious ______ how living things on the earth exactly began.

   A. in        B. at       C. of      D. about

people have always been curious ______ how living things on the earth exactly began.

   A. in        B. at       C. of      D. about