The first computer made available for commercial use was

Several early computers were built as one-off research or military machines and were never sold to outside customers. The first computer that was actually manufactured and sold as a product to government agencies and businesses, making it commercially available rather than a single custom-built machine, was completed in 1951 by the same engineers who had earlier built one of the first general-purpose electronic computers.

An early stored-program computer built at a British university in 1949 was groundbreaking as one of the first machines to run a stored program, but it remained a single research machine at that university and was never sold commercially. An earlier electromechanical computer completed in 1944 was built for a single university and government project and likewise was never offered for sale. The pioneering general-purpose electronic computer completed in 1945 proved that large-scale electronic computing was possible, but it too was a unique machine built for a specific government contract rather than a product manufactured for multiple paying customers.

When a question asks which computer was "made available for commercial use," look specifically for the machine that was manufactured and sold to multiple buyers, since being first, fastest, or most influential is not the same as being the first to be sold commercially.