Select the most appropriate word to fill in the blank.

______ there were no buses, we had to take a taxi.

Since

The most appropriate word to fill in the blank is since.

The word "since" is used to indicate a reason or cause. In this sentence, the reason we had to take a taxi is because there were no buses.

The other options are not as appropriate.

• The word "even if" is used to introduce a concession. It is not clear how the fact that there were no buses is a concession.
• The word "hence" is used to indicate a conclusion. It is not clear how the fact that there were no buses is a conclusion.
• The word "although" is used to introduce a contrast. It is not clear how the fact that there were no buses is a contrast.