He advised farmers to choose the best seed-heads , that had the best color .
A. 不填
B. ones
C. this
D. the ones
网友回答
A. 不填
B. ones
C. this
(答案→)D. the ones
解析：不定代词one是泛指，相当于a/an + 名词，ones相当于复数，特指时需要加the，句意：他建议农民选择最好的种子，有最好颜色的种子。横线后面为定语从句，应是特指，所以用the ones，ones指seed-heads，故选D。