In the conversation, the person 'Amit' asks 'Babita' if she knows any shop that sells affordable (inexpensive) sweaters.
Option C: 'Have you tried' completes the interrogative: 'Have you tried the factory outlets on the highway?' This sentence means that Babita is making a suggestion (in the form of a question). It relates to the conversation.
Hence C is the correct answer.
Option A: 'So you look at' isn't typical of a question form. It does not complete the required question in terms of structure. Hence A is wrong.
Option B: 'Are you knowing of' is grammatically incorrect.
Verbs that express a state of mind, like sense, know, think, do not have a continuous form: sensing, knowing, thinking. These forms function as adjectives. They do not refer to the action, like 'are you knowing'. Hence B is wrong.
Option D: 'Didn't you watch?' does not make a suggestion. The verb 'watch' refers to 'looking at' something, but over a period of time.
You 'watch' something that is shifting or changing, like 'watching a movie', 'watching birds'. It does not refer to looking at a shop, which is still. Hence D is an incorrect option.