The correct answer is ne la connaît.
First of all, you need to use the word NE to denote that it is the negative form of the verb (the questions is - Do you know Marine? and the answer translates as No, I do not know her). Then, you need to use the pronoun LA because Marine is a girl (LE is for males).
The third option is incorrect because you shouldn't use the verb sait (to know), but rather connaît (to be familiar with - although both translate the same). The fourth and the fifth options are incorrect (they don't have NE).
