Dear Hesham
The early war German A and B-types are a big puzzle. In those days the exact designation of a type or subtype of aircraft apparently didn't matter, and mostly the aircraft were designated simply as a A- or B-type.
Since 1911 the Otto-Flugzeugwerke built a number of different B-types. We can find reference to two of these as B I, but I don't know if this is a posterior designation or not.
I found the following references:
Kroschel & Stützer, Die deutschen Militärflugzeuge 1910-1918 (1994): B I with Rapp R I, 100 hp (max. speed 110 km/h), or with Mercedes (Daimler) D II, 120 hp (max. speed 135 km/h). Both span 14,5 m and enght 7,8 m. Built in 1914.
Lange, Typenhandbuch der deutschen Luftfahrttechnik (1986): Apparently the same planes, also built in 1914, but designated simply as B-types. The one with a Rapp engine (150 hp) was a two bay biplane, and the other (with a D III) was a three bay biplane.
Gray & Thetford, German Aircraft of the First World War (1970): On pages 494 and 495 photographs of an "Otto B 100 hp Rapp 1914" and "Otto B I 1914", two and three bay versions.
A little confusing, isn't it?