Step 1: Analyze Each Blank in the Sentence
- The correct preposition is "across" as the dog is running across the road.
- The correct preposition is "towards" as the dog is running toward its master.
- The correct preposition is "by", meaning the master was standing near the tree.
- The correct preposition is "in", referring to the rain.
Step 2: Final Answer
The correct set of prepositions is "across," "towards," "by," and "in."
This matches with option (C) f, g, e, b.