Which sentence effectively uses conjunctions to join two sentences into one?

Question

The detective followed the suspect. He disappeared into the crowded subway station.
The detective followed the suspect, but he disappeared into the crowded subway station.
The detective followed the suspect; he disappeared into the crowded subway station.
The detective followed the suspect. Surprisingly, he disappeared into the crowded subway station.

Answer 1

The sentence that effectively uses conjunctions to join two sentences into one is:

"The detective followed the suspect, but he disappeared into the crowded subway station."

This sentence uses the conjunction "but" to connect the two thoughts.