Question #N1263

Although a few people have claimed to be the inventor of the modern bicycle, it was Kirkpatrick Macmillan who actually invented the velocipede, a forerunner of the modern bicycle. Macmillan, a Scottish blacksmith, built his velocipede in 1839, using wooden wheels. The velocipede was powered by the rider's feet and could only travel in a straight line. It was a very basic machine. However, it was a crucial step in the development of the modern bicycle, which was invented several years later.

Which choice most effectively combines the sentences at the underlined portion without changing the meaning?
A. However, it was a crucial step in the development of the modern bicycle.
B. However, it was a very basic machine, a crucial step in the development of the modern bicycle.
C. However, it was a very basic machine, which was a crucial step in the development of the modern bicycle.
D. However, it was a very basic machine, but it was a crucial step in the development of the modern bicycle.