Read the passage.
These trains were not toys, and they were detailed models, and they were built to try out ideas. For real trains.
What is the best way to combine these incorrect sentences into one complete sentence?

a. These trains were not toys. They were detailed models. They were built to try out ideas. The ideas were for real trains.
b. These trains were not toys, they were detailed models, they were built to try out ideas for real trains.
c. These trains were toys and detailed models, and they were built to try out ideas for real trains.
d. These trains were not toys; they were detailed models built to try out ideas for real trains.