1. Seeing the policeman, he ran away.
2. When he saw the policeman, he ran away.
3. As soon as he saw the policeman, he ran away.
(Which one is similar to #1, #2 or #3?)
All three mean the same thing. 2 and 3 are better, though, and are used about equally, I think.
To determine which sentence is similar to sentence #1, let's analyze the given options:
1. "Seeing the policeman, he ran away."
2. "When he saw the policeman, he ran away."
3. "As soon as he saw the policeman, he ran away."
In sentence #1, the phrase "Seeing the policeman" is used as a participial phrase at the beginning of the sentence to describe the subject (he). This construction is considered a participial phrase construction.
Looking at the other options, sentence #2 begins with the subordinate conjunction "When," indicating that it is a dependent clause construction, while sentence #3 starts with the subordinating conjunction "As soon as," signaling a subordinate clause construction.
Therefore, the sentence most similar to sentence #1 is sentence #2: "When he saw the policeman, he ran away." Both sentence #1 and #2 use a similar structure to present the sequence of events by combining a dependent clause (the clause starting with "Seeing the policeman" or "When he saw the policeman") and an independent clause ("he ran away").