The word 'groundbreaking' (Line 3, ParA.) can be best replaced by______.
A.pioneering
B.evolutionary
C.unimaginable
D.epoch-making

A.A.pioneering
B.evolutionary
C.unimaginable

【参考答案】

A
解析：语义理解题。根据上文内容：虽然通过物种间的细胞核移植来完成一次受孕既费时且难度较大，可一旦成功，就能够......

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