1.Jack is at the market shopping for fruit,请问此句中

1.Jack is at the market shopping for fruit,请问此句中
的 shopping 能否去掉?for 能否换成to buy
2..help him check for mistakes.请问check 是及物动词呀,为什么要加for
3.1the cold weather made some birds fly south( for the winter).请问括号内的能不能去掉?为什么?另译这个句子.
4.请问northern 和north都能做形容词,两者有什么区别?