The words that are underlined in sentence 2 are <em>were really cool. </em>This type of language, which we usually use in everyday conversations with our friends, isn't used in informational texts, i.e. texts that give us information about a certain topic. Instead, we should use more formal language. The best substitute would be the words<em> </em><em>had great value.</em><em> </em>
Option A is incorrect because it also contains informal language (<em>totally useful - very useful</em> would be better).
Option C also isn't formal enough (<em>had a ton of uses - had many uses</em> is a better version).
Option D is incorrect because the given combination of words isn't correct. Something can't be <em>way important</em>. It can just be <em>very important.</em>
