The correct option is B hardly
The given options are all adverbs of frequency. Frequency adverbs describe how often something occurs, or takes place.
The words 'always', 'often' and 'regularly' are all positive adverbs. 'Always' means 'at all times', 'often' and 'regularly' mean 'many times'. These words cannot be used here, as each would contradict with the second part of the sentence: "I prefer to google everything".
The speaker means to say that he/she does not use the encyclopedia much, because he/she finds most answers on google.
The adverb 'hardly' means 'only just' or 'not much'. It is the most suitable option for the given sentence. It completes the sentence in meaning. Hence C is the correct option and the rest are incorrect.