context: During the First World War, the caliber of artillery on German submarines increased to 150 mm. The German “UB-1” and “UC-1” built in 1915 had one machine gun. The German "U-87" built in 1916 had one 105-mm gun. The German “U-139” built in 1917 had two 150-mm guns (see illustration) [4].
question: How many machine guns did the German “UB-1” and “UC-1” have built in 1915?
answers.text: one