She is walking along ___ the road.

In the sentence "She is walking along the road," the word "along" functions as a Preposition. A preposition shows the relationship between a noun or pronoun (in this case, "the road") and another word in the sentence (the verb "walking"). "Along" indicates movement or position in a line or path, specifying how the action relates to the object.

• "to" is also a preposition, but the question asks for the part of speech of "along".
• "Adjective" is incorrect; adjectives modify nouns or pronouns.
• "Conjunction" is incorrect; conjunctions join words, phrases, or clauses.