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:
Punjab,_Pakistan

Context:
Despite its tropical wet and dry climate, extensive irrigation makes it a rich agricultural region. Its canal-irrigation system established by the British is the largest in the world. Wheat and cotton are the largest crops. Other crops include rice, sugarcane, millet, corn, oilseeds, pulses, vegetables, and fruits such as kinoo. Livestock and poultry production are also important. Despite past animosities, the rural masses in Punjab's farms continue to use the Hindu calendar for planting and harvesting.

Question:
Who built Punjab's irrigation system?

the British