Question 17: Choose the correct answer in each sentence. There are a number of free Web-based ——that provide tips for locating information in historical databases.
Need to fill in the blank with a noun because before there is a preposition followed by 2 adjectives. The noun “tutor” and the gerund “tutoring” do not match because “a number of” must be a plural noun.
There are many tutorial pages on the website for free, providing tips for finding information on historical databases.