题干
While working in the country, the students ______ a lot of knowledge about plant.
A：looked up
B：picked up
C：put up
D：called up
答案(点此获取答案解析）
B
While working in the country, the students ______ a lot of knowledge about plant.
A：looked up
B：picked up
C：put up
D：called up
的切线方程是 （ ）
