Question

she can swim very good还是she can swim very well

Answer 1

应该是She can swim very well.

主要是good 和well的用法区别：
1. good 是个形容词，可以左定语（修饰名词，用于名词前）：
如 good boy, good friend
还可以做表语：如 I‘m good.
2. well 是个副词，主要修饰动词，放在动词的后面。如，play football well 篮球打得好
catch the ball well 熟练地接球
本题well 修饰swim, 放在swim之后，swim well 游泳游得好，而very 也是副词，可以用来修饰副词well. swim very well 游得非常好。

Answer 2

She can swim very well用副词well 修饰动词swim

Answer 3

第1句是错的，第2句是对的。