You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Pub

Context:
Strictly the term refers to the pump itself, which is normally manually operated, though electrically powered and gas powered pumps are occasionally used. When manually powered, the term "handpump" is often used to refer to both the pump and the associated handle.

Question:
Along with electricity, what sometimes powers beer pumps that aren't operated by hand?

gas