The town was nearly empty because everyone was watching the championship on TV.
The best way to combine these sentences is to use the conjunction "because".
Last night after the washer broke and flooded the basement, it took us an hour to clean up.
Adding the word after creates a dependent clause which then must be connected to the independent clause to create on sentence.
A little white dog, which belonged to the neighbors, was sitting on the front door.
Changing the second sentence into an adjectival clause allows the two sentences to be combined.
Rosie wanted to go to the lake with us, but she got sick and couldn't go.
Adding a coordinating conjunction (but), allows for both of these sentences to be joined together as a compound sentence.
Istanbul, the biggest city in Turkey, used to be called Constantinople.
By changing the first sentence into an appositive phrase, it allows for the sentences to be easily combined.
