My parents want me to get further study to be ________ an engineer _______ a scientist, ________ I would like to be a famous surgeon doctor.
A:neither; nor; and
B:either; or; but
C:not only; but; so
D:both; and; or
因式分解:a3﹣4a= ____.
水圈是地球的外部圈层中( )
下列说法中正确的是( )