The correct word to fill in the blank is "by." The sentence should read: "Most of the guests arrived for the concert by bus."
Explanation: In this context, the preposition "by" is used to indicate the means of transportation. It is a common preposition used to describe how people travel. Thus, "by bus" correctly answers the sentence, whereas the other options do not fit the context regarding transportation methods.
"By" is the correct preposition to indicate the mode of transportation.
Context: The preposition "by" is commonly used to specify the mode of transportation. It is used to indicate how something is done or how someone travels, referring to the means or vehicle used for movement.
Usage of "By": "By" is typically used with modes of transportation such as "by car," "by train," "by bus," or "by plane." It highlights the method or vehicle used to get from one place to another.
Final Thought: The use of "by" is grammatically correct when referring to the means of transportation, helping to specify how travel or movement occurs in a sentence.